Ignore clang -Wall warning.

src/tests/deqp.gypi

@@ -28,6 +28,12 @@
         'angle_build_deqp_executables%' : 0,
         'angle_build_deqp_gtest_executables%' :0,
 
+        'clang_warning_flags':
+        [
+             # tcu::CommandLine has virtual functions but no virtual destructor
+            '-Wno-no-delete-non-virtual-dtor',
+        ],
+
         'conditions':
         [
             ['(OS=="win" or OS=="linux" or OS=="mac")',