Add rust default compilation flags.

Bug: 140725928
Test: m -j crosvm.experimental
Change-Id: I1674f099659957f024cce70341a6a69610118a69
diff --git a/rust/builder.go b/rust/builder.go
index 9109651..27eeec2 100644
--- a/rust/builder.go
+++ b/rust/builder.go
@@ -44,6 +44,8 @@
 
 func TransformSrcToBinary(ctx android.ModuleContext, mainSrc android.Path, deps PathDeps, flags Flags,
 	outputFile android.WritablePath, includeDirs []string) {
+	flags.RustFlags = append(flags.RustFlags, "-C lto")
+
 	transformSrctoCrate(ctx, mainSrc, deps, flags, outputFile, "bin", includeDirs)
 }
 
@@ -59,11 +61,13 @@
 
 func TransformSrctoStatic(ctx android.ModuleContext, mainSrc android.Path, deps PathDeps, flags Flags,
 	outputFile android.WritablePath, includeDirs []string) {
+	flags.RustFlags = append(flags.RustFlags, "-C lto")
 	transformSrctoCrate(ctx, mainSrc, deps, flags, outputFile, "staticlib", includeDirs)
 }
 
 func TransformSrctoShared(ctx android.ModuleContext, mainSrc android.Path, deps PathDeps, flags Flags,
 	outputFile android.WritablePath, includeDirs []string) {
+	flags.RustFlags = append(flags.RustFlags, "-C lto")
 	transformSrctoCrate(ctx, mainSrc, deps, flags, outputFile, "cdylib", includeDirs)
 }