Workaround GCC 9 bug.

spirv_glsl.cpp

@@ -292,7 +292,13 @@ static const char *vector_swizzle(int vecsize, int index)
 		{ ".x", ".y", ".z", ".w" },
 		{ ".xy", ".yz", ".zw", nullptr },
 		{ ".xyz", ".yzw", nullptr, nullptr },
+#if defined(__GNUC__) && (__GNUC__ == 9)
+		// This works around a GCC 9 bug, see details in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90947.
+		// This array ends up being compiled as all nullptrs, tripping the assertions below.
+		{ "", nullptr, nullptr, "$" },
+#else
 		{ "", nullptr, nullptr, nullptr },
+#endif
 	};
 
 	assert(vecsize >= 1 && vecsize <= 4);