Revert "[lld] Add support for other demanglers other than Itanium"

This reverts commit e60d6dfd5acdc821d391ad5af2c706397bdfd36a.

clang-ppc64le-rhel buildbot failed (https://lab.llvm.org/buildbot#builders/57/builds/13424):

    tools/lld/MachO/CMakeFiles/lldMachO.dir/Symbols.cpp.o: In function `lld::demangle(llvm::StringRef, bool)':
    Symbols.cpp:(.text._ZN3lld8demangleEN4llvm9StringRefEb[_ZN3lld8demangleEN4llvm9StringRefEb]+0x90): undefined reference to `llvm::demangle(std::string const&)'

1 files changed, 3 insertions, 8 deletions

diff --git a/lld/include/lld/Common/Strings.h b/lld/include/lld/Common/Strings.h
index ece801892767..71126f615017 100644
--- a/lld/include/lld/Common/Strings.h
+++ b/lld/include/lld/Common/Strings.h
@@ -12,19 +12,14 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
-#include "llvm/Demangle/Demangle.h"
 #include "llvm/Support/GlobPattern.h"
 #include <string>
 #include <vector>
 
 namespace lld {
-// Returns a demangled symbol name. If Name is not a mangled name, it returns
-// name.
-inline std::string demangle(llvm::StringRef symName, bool shouldDemangle) {
-  if (shouldDemangle)
-    return llvm::demangle(symName.str().c_str());
-  return std::string(symName);
-}
+// Returns a demangled C++ symbol name. If Name is not a mangled
+// name, it returns name.
+std::string demangleItanium(llvm::StringRef name);
 
 std::vector<uint8_t> parseHex(llvm::StringRef s);
 bool isValidCIdentifier(llvm::StringRef s);