Meson.build: How can find_program() be combined with run_command() in a subproject?

I think I’ve found an acceptable solution myself. It seems this is an issue only
when --wrap-mode=forcefallback. If so, if gperf.found() in fontconfig/meson.build
can be changed to

if gperf.found() and get_option('wrap_mode') != 'forcefallback'

I’ve filed fontconfig issue 462.