John's revert of my removal commit dragged back a bunch of cygwin/sunos
cruft, as well as re-adding RegExp.cpp to the host libshared, that we don't
need.
Instead, remove this and add libgnuregex_build to just the tools/keymap
link alongside the FreeBSD gnuregex case.
It was needed on macOS for a time when BUrl used regexes for parsing.
Now it does not, and so we can remove libshared's RegExp from build
libshared, and thus also libgnuregex.
Fixes#12710.
Signed-off-by: Augustin Cavalier <waddlesplash@gmail.com>
I fixed the modifications to the Jamfiles in src/bin, they were all wrong
in the patch.
