fix(windows): compile memset_shim to real .o via get_compiler() to fix MinGW link

compile("memset_shim") produces libmemset_shim.a, not memset_shim.o, so the
previous cargo:rustc-link-arg pointed at a file that never exists. Switching to
get_compiler().to_command() compiles memset_s_shim.c directly to a .o file at
a known OUT_DIR path and passes it as a positional linker arg. A positional .o
is always included unconditionally, which also resolves the archive-extraction
ordering issue where -l flags only pull symbols that are already undefined at
that point in the link command.

src-tauri/build.rs

@@ -11,20 +11,27 @@ fn main() {
     let target_env = std::env::var("CARGO_CFG_TARGET_ENV").unwrap_or_default();
 
     if target_os == "windows" && target_env == "gnu" {
-        let out_dir = std::env::var("OUT_DIR").unwrap();
-        let obj_path = format!("{}/memset_shim.o", out_dir);
+        let out_dir = std::env::var("OUT_DIR").expect("OUT_DIR not set");
+        let obj_path = format!("{out_dir}/memset_s_shim.o");
 
-        cc::Build::new()
-            .file("memset_s_shim.c")
-            .define("WIN32", None)
-            .define("__WIN32__", None)
-            .out_dir(&out_dir)
-            .compile("memset_shim");
+        // Compile directly to a .o file and link it as a positional linker arg.
+        // This sidesteps the static-archive ordering problem: a bare -l flag only
+        // pulls symbols that are already undefined at that point in the link,
+        // but libsodium's reference to memset_explicit comes later. A positional
+        // object file is always included unconditionally.
+        let compiler = cc::Build::new().get_compiler();
+        let status = compiler
+            .to_command()
+            .args(["-DWIN32", "-D__WIN32__", "-c"])
+            .arg("-o")
+            .arg(&obj_path)
+            .arg("memset_s_shim.c")
+            .status()
+            .expect("failed to invoke C compiler for memset_s_shim.c");
+        assert!(status.success(), "failed to compile memset_s_shim.c");
 
         println!("cargo:rerun-if-changed=memset_s_shim.c");
-        // Directly link the object file instead of using -l flag
-        // This ensures the symbol is available regardless of link order
-        println!("cargo:rustc-link-arg={}", obj_path);
+        println!("cargo:rustc-link-arg={obj_path}");
     }
 
     tauri_build::build()