[docs] Remove a stale and confusing section from GettingStarted

The mentioned environment variable doesn't appear to have any use in the LLVM repository.  If it is still relevant for clang, we can consider adding it to the clang getting started page.

Patch inspired by documentation work by Ben Nathanson at the LLVM Bloomberg sprint.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260037 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed