Add force no external validation path to HLSL as well.

test_shaders.py

@@ -97,7 +97,7 @@ def cross_compile_msl(shader):
 
 def validate_shader_hlsl(shader):
     subprocess.check_call(['glslangValidator', '-e', 'main', '-D', '-V', shader])
-    if os.path.exists('fxc'):
+    if (not force_no_external_validation) and os.path.exists('fxc'):
         subprocess.check_call(['fxc', shader])
 
 def cross_compile_hlsl(shader):