meson's `cpp_args` option is defined only if it detects a C++ compiler,
otherwise we get an error:
../test/fuzz/meson.build:56:28: ERROR: Tried to access unknown option 'cpp_args'.
Prompted by #29972, because right now it's practically impossible to pass
-fno-sanitize=function to the fuzzer targets without some extensive
sed'ing.
This splits both c_args and cpp_args to separate arguments for
tools/meson-build.sh, because the other way would be to use `eval`, so
the space-separated but quoted strings passed to these options are not
split where they shouldn't, and I'd rather avoid using `eval` if
possible.
Also, this switches the positional arguments we pass to `meson setup`,
as they were in incorrect order (docs say it should be buildir followed
by sourcedir); meson is apparently clever enough to figure this out and
switch the arguments around if necessary, so it didn't complain.
Even though many of those scripts are very simple, it is easier to include
the header than to try to say whether each of those files is trivial enough
not to require one.
The ninja binary is deployed as `ninja-build` in older distros such as
RHEL 7/CentOS 7. Detect that and use `ninja-build` instead of `ninja`
when it's available.
This is a bit painful because a separate build of systemd is necessary. The
tests are guarded by tests!=false and slow-tests==true. Running them is not
slow, but compilation certainly is. If this proves unwieldy, we can add a
separate option controlling those builds later.
The build for each sanitizer has its own directory, and we build all fuzzer
tests there, and then pull them out one-by-one by linking into the target
position as necessary. It would be nicer to just build the desired fuzzer, but
we need to build the whole nested build as one unit.
[I also tried making systemd and nested meson subproject. This would work
nicely, but meson does not allow that because the nested target names are the
same as the outer project names. If that is ever fixed, that would be the way
to go.]
v2:
- make sure things still work if memory sanitizer is not available
v3:
- switch to syntax which works with meson 0.42.1 found in Ubuntu
