Compiling with ClangCL fails

[alichraghi]

ClangCL complains about this function being unused.

DirectXShaderCompiler/lib/Support/assert.cpp

Lines 14 to 19 in 848b7c4

	void llvm_assert_trap(const char *_Message, const char *_File, unsigned _Line,
	const char *_Function) {
	llvm::errs() << "Error: assert(" << _Message << ")\nFile:\n"
	<< _File << "(" << _Line << ")\nFunc:\t" << _Function << "\n";
	LLVM_BUILTIN_TRAP;
	}

Apparently -Wunused-function warning(error) is only enabled for ClangCL so CI never catched it.

DirectXShaderCompiler/cmake/modules/HandleLLVMOptions.cmake

Line 393 in 848b7c4

append("-Wnonportable-include-path -Wunused-function" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)

[damyanp]

Are you sure this is an error and not just a warning?

A PR addressing this would be welcome!