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/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