Rename gccCmd mingwCmd now that's all it's used for.

Bug: http://b/185257607
Test: treehugger
Change-Id: Ida079183828444f122ba6ea5662f63796677de7d
diff --git a/cc/gen.go b/cc/gen.go
index b152e02..3a1a0e2 100644
--- a/cc/gen.go
+++ b/cc/gen.go
@@ -204,7 +204,7 @@
 	headerFile := android.GenPathWithExt(ctx, "windmc", srcFile, "h")
 	rcFile := android.GenPathWithExt(ctx, "windmc", srcFile, "rc")
 
-	windmcCmd := gccCmd(flags.toolchain, "windmc")
+	windmcCmd := mingwCmd(flags.toolchain, "windmc")
 
 	ctx.Build(pctx, android.BuildParams{
 		Rule:           windmc,