compiler: add warp_{cc,cxx}_in_uchroot
compiler: add warp_{cc,cxx}_in_uchroot

This wraps a compiler inside the uchroot environment, just as
lt_clang/lt_clang_cxx does.


Former-commit-id: 3e131a2d6611bc399fcb57a28cefd64a0a864652
Former-commit-id: 619fef1a297eb286351d1b5f506aa04afa5be736 [formerly f717362ba18760002b05ad921f3c27ad0863910f] [formerly c734235c5a173a8a590d8061bb69471318d4c24b [formerly 7db22df99f4898fa31be7ae466c0378e29faea0a]]
Former-commit-id: e82ab52c2858e3a10373c09851f9793da5196c59 [formerly 619e5423d45bd6c91127b4c84c3c3f63f3d1f6e6]
Former-commit-id: d363bcbde22866335d3d8cf169af912ecf3e81be
PolyJIT/benchbuild,PolyJIT/benchbuild,PolyJIT/benchbuild,PolyJIT/benchbuild