[llvm-zorg] Flang and MLIR PowerPC buildbot; removed double quoting

Currently the -DLLVM_ENABLE_PROJECTS flag is not being parsed correctly
because of double quoting resulting in '-DLLVM_ENABLE_PROJECTS="mlir"'.
This commit changes zorg to generate -DLLVM_ENABLE_PROJECTS=mlir which
works properly.

Differential Revision: https://reviews.llvm.org/D86219
1 file changed