bindgen: set -Wno-unknown-warning-option flag by default

	// clang: error: '-x c' after last input file has no effect [-Werror,-Wunused-command-line-argument]

	cflags = append(cflags, "-Wno-unused-command-line-argument")

	// LLVM_NEXT may contain flags that bindgen doesn't recognise. Turn off unknown flags warning.

	if ctx.Config().IsEnvTrue("LLVM_NEXT") {

	// The Clang version used by CXX can be newer than the one used by Bindgen, and uses warning related flags that

	// it cannot recognize. Turn off unknown warning flags warning.

	cflags = append(cflags, "-Wno-unknown-warning-option")

	}

	outputFile := android.PathForModuleOut(ctx, b.BaseSourceProvider.getStem(ctx)+".rs")