Delete the llvm submodule lockfile when configuring on the bots
Delete the llvm submodule lockfile when configuring on the bots

This should fix the periodic error that .git/modules/src/llvm/index.lock
exists on the mac slaves.

aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust