rust: Add stub support for rust_ffi modules

This adds stubs support for rust_ffi and rust_ffi_shared modules. Usage
should match current cc usage. The stubs generator leveraged is the cc
stubs generator.

Bug: 203478530
Test: m blueprint_tests
Change-Id: I043b9714a357cd5fe17c183ccdf86900f5172e0e
diff --git a/cc/builder.go b/cc/builder.go
index 56b7139..5325116 100644
--- a/cc/builder.go
+++ b/cc/builder.go
@@ -851,6 +851,25 @@
 	return strings.Join(lines, "\n")
 }
 
+func BuildRustStubs(ctx android.ModuleContext, outputFile android.ModuleOutPath,
+	crtBegin, crtEnd android.Paths, stubObjs Objects, ccFlags Flags) {
+
+	// Instantiate paths
+	sharedLibs := android.Paths{}
+	staticLibs := android.Paths{}
+	lateStaticLibs := android.Paths{}
+	wholeStaticLibs := android.Paths{}
+	deps := android.Paths{}
+	implicitOutputs := android.WritablePaths{}
+	validations := android.Paths{}
+	groupLate := false
+
+	builderFlags := flagsToBuilderFlags(ccFlags)
+	transformObjToDynamicBinary(ctx, stubObjs.objFiles, sharedLibs, staticLibs,
+		lateStaticLibs, wholeStaticLibs, deps, crtBegin, crtEnd,
+		groupLate, builderFlags, outputFile, implicitOutputs, validations)
+}
+
 // Generate a rule for compiling multiple .o files, plus static libraries, whole static libraries,
 // and shared libraries, to a shared library (.so) or dynamic executable
 func transformObjToDynamicBinary(ctx android.ModuleContext,