Add bp2build for rust_protobuf module

We only supported bp2build for rust_protobuf_host because the non-host toolchain for rust is not checked in yet. aosp/2759750 changed a converted module from rust_protobuf_host to rust_protobuf and broke CI.

This CL adds bp2build support for rust_protobuf but makes the target incompatible with android os for now untilnon-host rust toolchain is checked in.

Bug: 301956497
Test: b build //build/make/tools/aconfig:all --config=android
Change-Id: I739896c79f32674000c2603e394f16860a6fc57d
diff --git a/rust/rust.go b/rust/rust.go
index 3b24484..250e398 100644
--- a/rust/rust.go
+++ b/rust/rust.go
@@ -1853,7 +1853,7 @@
 		procMacroBp2build(ctx, m)
 	} else if ctx.ModuleType() == "rust_binary_host" {
 		binaryBp2build(ctx, m)
-	} else if ctx.ModuleType() == "rust_protobuf_host" {
+	} else if ctx.ModuleType() == "rust_protobuf_host" || ctx.ModuleType() == "rust_protobuf" {
 		protoLibraryBp2build(ctx, m)
 	} else {
 		ctx.MarkBp2buildUnconvertible(bp2build_metrics_proto.UnconvertedReasonType_TYPE_UNSUPPORTED, "")