1f92557512
Remove directive, if present, from CFG_RUSTC_FLAGS. Fix #7898. (One alternative tack is to build up distinct CFG_TEST_RUSTC_FLAGS alongside CFG_RUSTC_FLAGS; but currently debug is the only --cfg flag ever added to CFG_RUSTC_FLAGS; the other contents of CFG_RUSTC_FLAGS are a mix of -Z flags and a few other switches like O, which seem to make sense to propogate to the tests.)