Rust library linking fixes

- Hide universal binary dependency for rust

Without a darwin_arm64 libstd prebuilt, many rust binaries are not
possible to build as a universal binary anyway. This fixes an
intermediate error with compiling rust FFI targets, where C++ shared
library dependencies for both architectures were combined into the same
linker command.

There is still an outstanding problem with C++ executable targets that
include rust FFI library targets, as the rust FFI library targets
fail to find a proper libstd to build the arm64 side of the universal
executable.

- Use dynamic_lib instead of soname

This matches similar logic in cc/library.go : linkerFlags for including
shared libraries.

Bug: 291830024
Test: m libkmr_cf_ffi (when enabled for darwin)
Change-Id: I1d6b6a7855c6649b93ab6592ea43b17c6e37b3a3

rust/rust.go

@@ -1224,6 +1224,11 @@ func (mod *Module) depsToPaths(ctx android.ModuleContext) PathDeps {
 		if _, exists := skipModuleList[depName]; exists {
 			return
 		}
+
+		if depTag == android.DarwinUniversalVariantTag {
+			return
+		}
+
 		if rustDep, ok := dep.(*Module); ok && !rustDep.CcLibraryInterface() {
 			//Handle Rust Modules
 			makeLibName := rustMakeLibName(ctx, mod, rustDep, depName+rustDep.Properties.RustSubName)