meson: omit bash completion, with custom prefix
In order for bash completions to work, they must be installed in the respective folder. Often that folder is writable only by root.
In order words, using a command line the following now is successful, providing indicative warning message.
meson builddir --prefix pwd
/inst
...
meson.build:140: WARNING: User provided prefix '.../inst' differs from bash-completion one '/usr'. Disabling completion.
/cc @pq can you confirm this fixes the issue on your end? Fwiw other meson projects (systemd) suffer from this problem.