GCC 7.5 errors in WriteSwitch

Source/Core/VideoCommon/UberShaderCommon.h

@@ -39,12 +39,15 @@ std::string BitfieldExtract(std::string_view source)
                      static_cast<u32>(BitFieldT::NumBits()));
 }
 
-template <auto last_member>
+template <auto last_member, typename = decltype(last_member)>
 void WriteSwitch(ShaderCode& out, APIType ApiType, std::string_view variable,
                  const EnumMap<std::string_view, last_member>& values, int indent, bool break_)
 {
   const bool make_switch = (ApiType == APIType::D3D);
 
+  // The second template argument is needed to avoid compile errors from ambiguity with multiple
+  // enums with the same number of members in GCC prior to 8.  See https://godbolt.org/z/xcKaW1seW
+  // and https://godbolt.org/z/hz7Yqq1P5
   using enum_type = decltype(last_member);
 
   // {:{}} is used to indent by formatting an empty string with a variable width