Parallelize singleton execution

Bug: 281536768
Test: manual, presubmits
Change-Id: I57fdc76ba6b277e88e196b506af87127a530fd37
diff --git a/cc/compdb.go b/cc/compdb.go
index ea12443..617be1a 100644
--- a/cc/compdb.go
+++ b/cc/compdb.go
@@ -32,7 +32,7 @@
 // make SOONG_GEN_COMPDB=1 nothing to get all targets.
 
 func init() {
-	android.RegisterSingletonType("compdb_generator", compDBGeneratorSingleton)
+	android.RegisterParallelSingletonType("compdb_generator", compDBGeneratorSingleton)
 }
 
 func compDBGeneratorSingleton() android.Singleton {