Parallelize singleton execution

Bug: 281536768
Test: manual, presubmits
Change-Id: I57fdc76ba6b277e88e196b506af87127a530fd37
diff --git a/cc/ndk_sysroot.go b/cc/ndk_sysroot.go
index dffc6c6..0cf21b6 100644
--- a/cc/ndk_sysroot.go
+++ b/cc/ndk_sysroot.go
@@ -66,7 +66,7 @@
 	ctx.RegisterModuleType("ndk_library", NdkLibraryFactory)
 	ctx.RegisterModuleType("versioned_ndk_headers", versionedNdkHeadersFactory)
 	ctx.RegisterModuleType("preprocessed_ndk_headers", preprocessedNdkHeadersFactory)
-	ctx.RegisterSingletonType("ndk", NdkSingleton)
+	ctx.RegisterParallelSingletonType("ndk", NdkSingleton)
 }
 
 func getNdkInstallBase(ctx android.PathContext) android.InstallPath {