Stop defining negative versions of some lit feature keywords: zlib/nozlib, asan/not_asan, msan/not_msan, ubsan/not_ubsan.
We still have two other ways to express the absence of a feature.
First, we have the '!' operator to invert the sense of a keyword. For
example, given a feature that depends on zlib being unavailable, its
test can say:
Second, if a test doesn't play well with some features, such as
sanitizers, that test can say:
UNSUPPORTED: asan, msan
The different ways of writing these exclusions both have the same
technical effect, but have different implications to the reader.