meson: find_program('gdbus-codegen') directly

meson: find_program('gdbus-codegen') directly

gio.pc variable is a bit bogus in context of cross-compilation, since it
contains an absolute path, relative to the sysroot directory. On Fedora, it ends
up as:
/usr/x86_64-w64-mingw32/sys-root/mingw/lib/pkgconfig/usr/bin/gdbus-codegen
path which does not exist because it is not shipped by Fedora mingw
packages.

Instead, we can rely on meson find_program() behaviour to do a better
job based on its search order and capabilities.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-ID: <20241008125028.1177932-14-marcandre.lureau@redhat.com>