i18n module only checks for gettext and misses xgettext

Describe the bug We have a configure file in our build that uses i18n.merge_file. In the users log we saw

Program gettext found: YES (/usr/bin/gettext)

But when Meson reached the i18n.merge_file this error was spit out.

WARNING: Gettext not found, all translation targets will be ignored.

To Reproduce

It took some time to figure out, but the user is on Debian stable, but the issue was that they had gettext-base installed that contains /usr/bin/gettext but xgettext that i18n.merge_file requires is actually in the gettext package.

Expected behavior

It would have been awesome if when detecting the gettext binary, meson would check for xgettext as well if i18n.merge_file is in use. If it couldn’t find it, it would be much nicer if it would mention the executable it was looking for as I had to dig through the meson source to figure out what it was complaining about as the user already verified that they had /usr/bin/gettext installed.

system parameters

The user was on Debian stable with meson 0.56.2, but their system isn’t relevant here out side of the gettext-base was installed but gettext was not installed scenario.

[eli-schwartz]

I opened a PR which fixes this in two ways:

• it actually checks for each tool which is actually used, and logs whether it is found. The WARNING: Gettext not found [...] is still printed, but immediately beforehand it also mentions the exact tool name it is looking for, so that should presumably be easy to interpret.
• merge_file is actually required to work now, because it’s unreasonable to expect it to be able to be disabled.

[inigomartinez]

Thanks!