Only build append_negative_gtest_filter when it is used.

Change-Id: If6fec02fd8125b368ea83c99208575ac0d4a662b

test/test_libvpx.cc

@@ -26,6 +26,7 @@ extern void vpx_dsp_rtcd();
 extern void vpx_scale_rtcd();
 }
 
+#if ARCH_X86 || ARCH_X86_64
 static void append_negative_gtest_filter(const char *str) {
   std::string filter = ::testing::FLAGS_gtest_filter;
   // Negative patterns begin with one '-' followed by a ':' separated list.
@@ -33,6 +34,7 @@ static void append_negative_gtest_filter(const char *str) {
   filter += str;
   ::testing::FLAGS_gtest_filter = filter;
 }
+#endif  // ARCH_X86 || ARCH_X86_64
 
 int main(int argc, char **argv) {
   ::testing::InitGoogleTest(&argc, argv);
@@ -55,7 +57,7 @@ int main(int argc, char **argv) {
     append_negative_gtest_filter(":AVX.*:AVX/*");
   if (!(simd_caps & HAS_AVX2))
     append_negative_gtest_filter(":AVX2.*:AVX2/*");
-#endif
+#endif  // ARCH_X86 || ARCH_X86_64
 
 #if !CONFIG_SHARED
 // Shared library builds don't support whitebox tests