treewide: internally avoid deprecated machine file uses of "pkgconfig"

[eli-schwartz]

We support this in a machine file:

[binaries]
pkgconfig = 'pkg-config'
pkg-config = 'pkg-config'

and you can use either one, because internally we look up both. If you only set one of them, this plays awkwardly with setting $PKG_CONFIG, since we don't know which one you set in the machine file and the other one will be initialized from the environment instead.

In commit 22df45a we changed program lookup of config-tool style dependencies to use the regular tool names and only fall back on the strange internal names. This affected the pkg-config class too.

The result is that instead of preferring pkgconfig = followed by $PKG_CONFIG followed by pkg-config =, we inverted the lookup order. This is a good idea anyway, because now it behaves consistently with find_program('pkg-config').

Unfortunately, we documented the wrong name in a bunch of places, and also used the wrong name in various testsuite bits, which meant that if you set $PKG_CONFIG and then ran the testsuite, it would fail.

Correct these references, because they are buggy.

[eli-schwartz]

/cc @mhmdanas

[triallax]

Thanks for the quick fix, can confirm that with this the tests pass. Cheers!

[xclaesse]

LGTM, but CI seems unhappy.

Should we also actually deprecate pkgconfig? Something along the line of d5f4228

[eli-schwartz]

LGTM, but CI seems unhappy.

The failing test is... interesting.

It happens only during cross builds, and it happens because we test that pkgconfig generation works by inserting a manual requires on 'glib-2.0' as a string.

The test case uses find_program('pkg-config', required: false), which previously found nothing from the cross file, but now finds something because the lookup value in the global cross file for tests is pkgconfig -> pkg-config. This means that:

pkgconfig = find_program('pkg-config', required: false)

env = environment()
env.prepend('PKG_CONFIG_PATH', meson.current_build_dir() / 'meson-private')

test(
  'pkgconfig-validation',
  pkgconfig,
  args: ['--validate', 'simple'],
  env : env,
)

now runs a cross pkg-config test:

PKG_CONFIG_PATH='/__w/meson/meson/b 752d8a5fd7/meson-private' /usr/bin/x86_64-w64-mingw32-pkg-config --validate simple

whereas before, it ran a native pkg-config test:

PKG_CONFIG_PATH='/__w/meson/meson/b 752d8a5fd7/meson-private' /usr/bin/pkg-config --validate simple

Naturally, the cross environment doesn't have a mingw glib-2.0 installed...