Make LLD work even if the current directory is not writable.

llvm-svn: 301423
diff --git a/lld/ELF/Filesystem.cpp b/lld/ELF/Filesystem.cpp
index 0b9cea9..b63d521 100644
--- a/lld/ELF/Filesystem.cpp
+++ b/lld/ELF/Filesystem.cpp
@@ -70,5 +70,7 @@
 // is called. We use that class without calling commit() to predict
 // if the given file is writable.
 std::error_code elf::tryCreateFile(StringRef Path) {
+  if (Path.empty())
+    return std::error_code();
   return FileOutputBuffer::create(Path, 1).getError();
 }