Reduce the LockFileManager timeout, and provide unsafeRemoveLockFile

5 minutes is an eternity, so try to strike a better balance between
waiting long enough for any reasonable module build and not so long that
users kill the process because they think it's hanging.

Also give the client a way to delete the lock file after a timeout.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228603 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/LockFileManager.h

@@ -77,6 +77,10 @@ public:
 
   /// \brief For a shared lock, wait until the owner releases the lock.
   WaitForUnlockResult waitForUnlock();
+
+  /// \brief Remove the lock file.  This may delete a different lock file than
+  /// the one previously read if there is a race.
+  std::error_code unsafeRemoveLockFile();
 };
 
 } // end namespace llvm