Enable goma in soong

When the UseGoma flag is set, put all rules except the C compilation
rule in an externally defined local_pool, which will have been created
by kati.  The gomacc wrapper will already be in the CC_WRAPPER
environment variable.

Bug: 31142427
Change-Id: I699d4edff2e302eee398dad8692ceb14721a628c
diff --git a/cc/ndk_library.go b/cc/ndk_library.go
index b0fd398..37ce268 100644
--- a/cc/ndk_library.go
+++ b/cc/ndk_library.go
@@ -28,7 +28,7 @@
 var (
 	toolPath = pctx.SourcePathVariable("toolPath", "build/soong/cc/gen_stub_libs.py")
 
-	genStubSrc = pctx.StaticRule("genStubSrc",
+	genStubSrc = pctx.AndroidStaticRule("genStubSrc",
 		blueprint.RuleParams{
 			Command:     "$toolPath --arch $arch --api $apiLevel $in $out",
 			Description: "genStubSrc $out",