Allow .o files as srcs.

Test: m nothing
Test: TreeHugger
Bug: 134581881
Bug: 137267623

Change-Id: I26307dd1129e58878f0468da3b61c53f074bd674
diff --git a/cc/builder.go b/cc/builder.go
index 89c418b..14b979e 100644
--- a/cc/builder.go
+++ b/cc/builder.go
@@ -411,6 +411,9 @@
 				},
 			})
 			continue
+		case ".o":
+			objFiles[i] = srcFile
+			continue
 		}
 
 		var moduleCflags string