Since all our python scripts have a proper python3 shebang, there is no benefit
to letting meson autodetect them. On linux, meson will just uses exec(), so the
shebang is used anyway. The only difference should be in how meson reports the
script and that the detection won't fail for (most likely misconfigured)
non-UTF8 locales.
Closes#5855.
This is useful on systems like NixOS, where python3 is not in
/usr/bin/python3 as well as for people using alternative ways to
install python such as virtualenv/pyenv.
Shell scripts should be executable so that meson reports their
invocation succinctly (does not print 'sh' '-e').
Python scripts should not be executable so that meson does the
detection of the right python binary itself.
Add -u everywhere to catch potential errors.
This is quite messy. I think libtool might have been using something
like -Wl,--whole-archive, but I don't think meson has support for that.
For now, just recompile all the sources for linking into libsystemd
directly. This should not matter much for efficiency, since it's a
few small files.
