Temporarily remove toolchain/ from androidmk_denylist.go

There are defensive `Android.mk` files present in several top-level
toolchain/ projects. Enforcing the denylist strictly breaks several
builds, so this change temporarily relaxes that by removing our
directories from the list.

Test: Run Rust's test_compiler.py
Change-Id: Ic00a305b78485543d098aeea42c2d2b93f979430

ui/build/androidmk_denylist.go

@@ -30,7 +30,8 @@ var androidmk_denylist []string = []string{
 	"libcore/",
 	"libnativehelper/",
 	"pdk/",
-	"toolchain/",
+	// Add back toolchain/ once defensive Android.mk files are removed
+	//"toolchain/",
 }
 
 func blockAndroidMks(ctx Context, androidMks []string) {