clean up stale LLD checkouts on mac and linux bots

tools/clang/scripts/update.py

Index: tools/clang/scripts/update.py
diff --git a/tools/clang/scripts/update.py b/tools/clang/scripts/update.py
index cfe94cb837cc79c078b41ff5fe1289867d1ad608..dbe0fdf5b5ab64bcc88ac8734fd5d84073756c1d 100755
--- a/tools/clang/scripts/update.py
+++ b/tools/clang/scripts/update.py
@@ -461,6 +461,10 @@ def UpdateClang(args):
   Checkout('Clang', LLVM_REPO_URL + '/cfe/trunk', CLANG_DIR)
   if sys.platform == 'win32' or use_head_revision:
     Checkout('LLD', LLVM_REPO_URL + '/lld/trunk', LLD_DIR)
+  elif os.path.exists(LLD_DIR):
+    # In case someone sends a tryjob that temporary adds lld to the checkout,
+    # make sure it's not around on future builds.
+    RmTree(LLD_DIR)
   Checkout('compiler-rt', LLVM_REPO_URL + '/compiler-rt/trunk', COMPILER_RT_DIR)
   if sys.platform == 'darwin':
     # clang needs a libc++ checkout, else -stdlib=libc++ won't find includes