fix(windows): vendor audiopus_sys + patch libopus for clang-cl SIMD

cargo-xwin drives the Windows MSVC cross-compile via clang-cl, under
which CMake sets MSVC=1 — causing libopus 1.3.1's `if(NOT MSVC)` guards
to skip the per-file `-msse4.1` / `-mssse3` COMPILE_FLAGS that its x86
SIMD source files need. Clang-cl (unlike real cl.exe) still honors
Clang's target-feature system, so those files then fail to compile
with "always_inline function '_mm_cvtepi16_epi32' requires target
feature 'sse4.1'" errors across silk/NSQ_sse4_1.c, NSQ_del_dec_sse4_1.c,
and VQ_WMat_EC_sse4_1.c.

Earlier attempts to fix this downstream (cargo-xwin toolchain file,
override.cmake CMAKE_C_COMPILE_OBJECT <FLAGS> replace, CFLAGS env vars)
all failed because cargo-xwin rewrites override.cmake from scratch on
every `cargo xwin build` invocation and cmake-rs's -DCMAKE_C_FLAGS=
assembly happens before toolchain FORCE sets propagate.

Fixing it upstream at the source: vendor audiopus_sys 0.2.2 into
vendor/audiopus_sys, patch its bundled opus/CMakeLists.txt to introduce
an MSVC_CL var (true only when CMAKE_C_COMPILER_ID == "MSVC", i.e. real
cl.exe), and flip the eight `if(NOT MSVC)` SIMD guards to
`if(NOT MSVC_CL)`. Clang-cl then gets the GCC-style per-file flags and
the SSE4.1 sources build cleanly. Also flip the `if(MSVC)` global /arch
block at line 445 to `if(MSVC_CL)` so only cl.exe applies /arch:AVX and
clang-cl relies purely on per-file flags (no global/per-file mixing).

Wire via [patch.crates-io] in the workspace root Cargo.toml; the patch
is resolved relative to the workspace root as `vendor/audiopus_sys`.

Upstream context: xiph/opus#256, xiph/opus PR #257 (both stale).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/audiopus_sys/opus/celt/arm/armcpu.c

@@ -0,0 +1,187 @@
+/* Copyright (c) 2010 Xiph.Org Foundation
+ * Copyright (c) 2013 Parrot */
+/*
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions
+   are met:
+
+   - Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+
+   - Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
+   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+/* Original code from libtheora modified to suit to Opus */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef OPUS_HAVE_RTCD
+
+#include "armcpu.h"
+#include "cpu_support.h"
+#include "os_support.h"
+#include "opus_types.h"
+#include "arch.h"
+
+#define OPUS_CPU_ARM_V4_FLAG    (1<<OPUS_ARCH_ARM_V4)
+#define OPUS_CPU_ARM_EDSP_FLAG  (1<<OPUS_ARCH_ARM_EDSP)
+#define OPUS_CPU_ARM_MEDIA_FLAG (1<<OPUS_ARCH_ARM_MEDIA)
+#define OPUS_CPU_ARM_NEON_FLAG  (1<<OPUS_ARCH_ARM_NEON)
+
+#if defined(_MSC_VER)
+/*For GetExceptionCode() and EXCEPTION_ILLEGAL_INSTRUCTION.*/
+# define WIN32_LEAN_AND_MEAN
+# define WIN32_EXTRA_LEAN
+# include <windows.h>
+
+static OPUS_INLINE opus_uint32 opus_cpu_capabilities(void){
+  opus_uint32 flags;
+  flags=0;
+  /* MSVC has no OPUS_INLINE __asm support for ARM, but it does let you __emit
+   * instructions via their assembled hex code.
+   * All of these instructions should be essentially nops. */
+# if defined(OPUS_ARM_MAY_HAVE_EDSP) || defined(OPUS_ARM_MAY_HAVE_MEDIA) \
+ || defined(OPUS_ARM_MAY_HAVE_NEON) || defined(OPUS_ARM_MAY_HAVE_NEON_INTR)
+  __try{
+    /*PLD [r13]*/
+    __emit(0xF5DDF000);
+    flags|=OPUS_CPU_ARM_EDSP_FLAG;
+  }
+  __except(GetExceptionCode()==EXCEPTION_ILLEGAL_INSTRUCTION){
+    /*Ignore exception.*/
+  }
+#  if defined(OPUS_ARM_MAY_HAVE_MEDIA) \
+ || defined(OPUS_ARM_MAY_HAVE_NEON) || defined(OPUS_ARM_MAY_HAVE_NEON_INTR)
+  __try{
+    /*SHADD8 r3,r3,r3*/
+    __emit(0xE6333F93);
+    flags|=OPUS_CPU_ARM_MEDIA_FLAG;
+  }
+  __except(GetExceptionCode()==EXCEPTION_ILLEGAL_INSTRUCTION){
+    /*Ignore exception.*/
+  }
+#   if defined(OPUS_ARM_MAY_HAVE_NEON) || defined(OPUS_ARM_MAY_HAVE_NEON_INTR)
+  __try{
+    /*VORR q0,q0,q0*/
+    __emit(0xF2200150);
+    flags|=OPUS_CPU_ARM_NEON_FLAG;
+  }
+  __except(GetExceptionCode()==EXCEPTION_ILLEGAL_INSTRUCTION){
+    /*Ignore exception.*/
+  }
+#   endif
+#  endif
+# endif
+  return flags;
+}
+
+#elif defined(__linux__)
+/* Linux based */
+#include <stdio.h>
+
+opus_uint32 opus_cpu_capabilities(void)
+{
+  opus_uint32 flags = 0;
+  FILE *cpuinfo;
+
+  /* Reading /proc/self/auxv would be easier, but that doesn't work reliably on
+   * Android */
+  cpuinfo = fopen("/proc/cpuinfo", "r");
+
+  if(cpuinfo != NULL)
+  {
+    /* 512 should be enough for anybody (it's even enough for all the flags that
+     * x86 has accumulated... so far). */
+    char buf[512];
+
+    while(fgets(buf, 512, cpuinfo) != NULL)
+    {
+# if defined(OPUS_ARM_MAY_HAVE_EDSP) || defined(OPUS_ARM_MAY_HAVE_MEDIA) \
+ || defined(OPUS_ARM_MAY_HAVE_NEON) || defined(OPUS_ARM_MAY_HAVE_NEON_INTR)
+      /* Search for edsp and neon flag */
+      if(memcmp(buf, "Features", 8) == 0)
+      {
+        char *p;
+        p = strstr(buf, " edsp");
+        if(p != NULL && (p[5] == ' ' || p[5] == '\n'))
+          flags |= OPUS_CPU_ARM_EDSP_FLAG;
+
+#  if defined(OPUS_ARM_MAY_HAVE_NEON) || defined(OPUS_ARM_MAY_HAVE_NEON_INTR)
+        p = strstr(buf, " neon");
+        if(p != NULL && (p[5] == ' ' || p[5] == '\n'))
+          flags |= OPUS_CPU_ARM_NEON_FLAG;
+#  endif
+      }
+# endif
+
+# if defined(OPUS_ARM_MAY_HAVE_MEDIA) \
+ || defined(OPUS_ARM_MAY_HAVE_NEON) || defined(OPUS_ARM_MAY_HAVE_NEON_INTR)
+      /* Search for media capabilities (>= ARMv6) */
+      if(memcmp(buf, "CPU architecture:", 17) == 0)
+      {
+        int version;
+        version = atoi(buf+17);
+
+        if(version >= 6)
+          flags |= OPUS_CPU_ARM_MEDIA_FLAG;
+      }
+# endif
+    }
+
+    fclose(cpuinfo);
+  }
+  return flags;
+}
+#else
+/* The feature registers which can tell us what the processor supports are
+ * accessible in priveleged modes only, so we can't have a general user-space
+ * detection method like on x86.*/
+# error "Configured to use ARM asm but no CPU detection method available for " \
+   "your platform.  Reconfigure with --disable-rtcd (or send patches)."
+#endif
+
+int opus_select_arch(void)
+{
+  opus_uint32 flags = opus_cpu_capabilities();
+  int arch = 0;
+
+  if(!(flags & OPUS_CPU_ARM_EDSP_FLAG)) {
+    /* Asserts ensure arch values are sequential */
+    celt_assert(arch == OPUS_ARCH_ARM_V4);
+    return arch;
+  }
+  arch++;
+
+  if(!(flags & OPUS_CPU_ARM_MEDIA_FLAG)) {
+    celt_assert(arch == OPUS_ARCH_ARM_EDSP);
+    return arch;
+  }
+  arch++;
+
+  if(!(flags & OPUS_CPU_ARM_NEON_FLAG)) {
+    celt_assert(arch == OPUS_ARCH_ARM_MEDIA);
+    return arch;
+  }
+  arch++;
+
+  celt_assert(arch == OPUS_ARCH_ARM_NEON);
+  return arch;
+}
+
+#endif