This should fix the build after SVN r316178, which worked fine
on GCC 5.4, but failed on clang with errors like these:
MinGW.h:26:3: error: too few template arguments for class template 'StringSet'
StringSet<> ExcludeSymbols;
^
lld/Common/LLVM.h:28:30: note: template is declared here
template<typename T> class StringSet;
Don't forward declare and add the using directive in the main
lld/Common/LLVM.h header, but just qualify the class name
in MinGW.h instead.
llvm-svn: 316180
Martin Storsjo