Build cleanup: meson 0.50
Let's get rid of this one:
WARNING: Project specifies a minimum meson_version '>= 0.49.0' but uses features which were added in newer versions:
* 0.50.0: {'install arg in configure_file'}
F29 ships 0.51 as an update, U19.10 beta (which I've upgraded to) has it too.
@debarshir Could you please comment on the RHEL 7 / 8 versions of meson?
@chpe If your system is also recent enough, let's just bump the requirement to 0.50 instead of such hacks.
Indended for master only, no 0-58 backport.