LLVM_CONFIG, per the contents of toolkit/moz.configure, is tied to
--enable-stylo, but it currently is set on all types of builds. It
currently happens to work, but it's actually not meant to, and sure
enough, the fix for bug 1374727 exacerbates that.
So we create a new mozconfig.stylo file that enables stylo and sets
LLVM_CONFIG, such that only build types that do enable stylo have
LLVM_CONFIG set.
--HG--
extra : rebase_source : 01277a79951888046c0b8e29c61cfc3b049ee0f0