fix(android): -Wl,--exclude-libs,ALL + --no-whole-archive to stop symbol leak

llvm-nm on the crashing .so confirmed the research's smoking gun theory:

  000000000130c1f0 t _Z10__init_tcbP10bionic_tcbP18pthread_internal_t
  0000000000000000 a pthread_create.cpp
  0000000001331108 t pthread_create

All lowercase 't' (= LOCAL text symbols), zero UND dynamic references
for pthread_create. So rustc's link step is pulling bionic's own
pthread_create.cpp compilation unit out of libc.a as a whole-archive
inclusion and binding those symbols locally inside our .so, instead
of letting them stay UND and resolved against libc.so at dlopen time.

Rust's libstd thread::spawn then calls the LOCAL (broken) pthread_create
which calls the LOCAL __init_tcb with arguments set up for bionic's
static-executable layout — crashes at __init_tcb+4 with SEGV_ACCERR.

`-Wl,--exclude-libs,ALL` tells the linker to make symbols from static
archives NOT appear in the dynamic symbol table of the output .so.
`-Wl,--no-whole-archive` tells it to only pull archive objects that
satisfy undefined references, not include the whole archive blindly.

If this works, the symbol table should show pthread_create as UND
(or at least not locally bound) and the app should launch. If it
doesn't, the remaining fallback is the research's action #3 —
extract the C++ into its own upstream cdylib crate built with
cargo-ndk, and dlopen it from the Tauri cdylib at runtime.

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

desktop/src-tauri/build.rs

@@ -57,6 +57,15 @@ fn main() {
             .file("cpp/cpp_smoke.cpp")
             .compile("wzp_cpp_smoke");
 
+        // Per rust-lang/rust#104707 + the android-ndk advice: force the
+        // linker to keep bionic symbols (pthread_create, __init_tcb) as
+        // UND dynamic references resolved against libc.so at runtime,
+        // not bound locally from libc.a that cc-rs + cpp(true) drag in.
+        // llvm-nm confirmed these symbols were landing in our .so as
+        // LOCAL (lowercase t), which is exactly the bug.
+        println!("cargo:rustc-link-arg=-Wl,--exclude-libs,ALL");
+        println!("cargo:rustc-link-arg=-Wl,--no-whole-archive");
+
         // Copy libc++_shared.so from the NDK sysroot to gen/android jniLibs
         // so the runtime linker can find it at dlopen time (it's now in the
         // .so's NEEDED list thanks to cpp_link_stdlib("c++_shared") above).