GettingStarted: Add Git clone instructions for compiler-rt and test-suite

Contributed-by:  Thomas Schwinge  <thomas@codesourcery.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177841 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed