step D(android): compile cpp/getauxval_fix.c alongside hello.c

Fourth incremental variable. Adds the getauxval_fix.c shim from the
legacy wzp-android crate (which has been shipping with it for months
without issue) to our cc::Build on Android. The file defines a single
getauxval() function that delegates to bionic's real runtime
implementation via dlsym — this is needed because rustc links
compiler-rt's broken static getauxval stub that SIGSEGVs in .so
libraries loaded via dlopen (reads __libc_auxv which is NULL).

Not imported from Rust. Goal: verify that adding a second C static
archive (and especially one that overrides a libc-ish symbol) doesn't
regress the working build.

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

desktop/src-tauri/build.rs

@@ -16,17 +16,22 @@ fn main() {
     println!("cargo:rerun-if-changed=../../.git/refs/heads");
 
     // ─── Step A: single trivial cpp/hello.c compiled via cc::Build ─────────
-    // We deliberately add this on Android only so we can verify that the
-    // cc::Build → static archive → rustc-link pipeline itself does not
-    // regress the working build #17. cpp/hello.c defines `wzp_hello_stub`
-    // which is never called from Rust — if the crash comes back just from
-    // adding a tiny C static lib, we know the build pipeline is the issue.
+    // ─── Step D: also compile getauxval_fix.c (legacy wzp-android shim) ────
+    // getauxval_fix.c overrides the broken static getauxval stub that
+    // compiler-rt pulls in for Android targets. It's been shipping in the
+    // legacy wzp-android .so for months without issue, so including it here
+    // is low-risk — but it's an incremental variable we want to isolate.
     let target = std::env::var("TARGET").unwrap_or_default();
     if target.contains("android") {
         println!("cargo:rerun-if-changed=cpp/hello.c");
         cc::Build::new()
             .file("cpp/hello.c")
             .compile("wzp_hello");
+
+        println!("cargo:rerun-if-changed=cpp/getauxval_fix.c");
+        cc::Build::new()
+            .file("cpp/getauxval_fix.c")
+            .compile("getauxval_fix");
     }
 
     tauri_build::build()

desktop/src-tauri/cpp/getauxval_fix.c

@@ -0,0 +1,26 @@
+/* Override the broken static getauxval from compiler-rt/CRT.
+ *
+ * The static version reads from __libc_auxv which is NULL in shared libs
+ * loaded via dlopen, causing SIGSEGV in init_have_lse_atomics at load time.
+ * This version calls the real bionic getauxval via dlsym.
+ *
+ * Copied verbatim from crates/wzp-android/cpp/getauxval_fix.c — the legacy
+ * wzp-android crate has been using this shim successfully for months.
+ */
+#ifdef __ANDROID__
+#include <dlfcn.h>
+#include <stdint.h>
+
+typedef unsigned long (*getauxval_fn)(unsigned long);
+
+unsigned long getauxval(unsigned long type) {
+    static getauxval_fn real_getauxval = (getauxval_fn)0;
+    if (!real_getauxval) {
+        real_getauxval = (getauxval_fn)dlsym((void*)-1L /* RTLD_DEFAULT */, "getauxval");
+        if (!real_getauxval) {
+            return 0;
+        }
+    }
+    return real_getauxval(type);
+}
+#endif