[doc] Fix Getting Started typo.

This makes it easier for someone to copy-paste this line, change the path, and run the command.

Differential Revision: https://reviews.llvm.org/D49201

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@338254 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed