gdbus-codegen: test --interface-info-{header,body}

This test is rudimentary but better than nothing.

(Backport to glib-2-58: Fix minor merge conflict.)
11 jobs from backport-514-codegen-interface-info-glib-2-58 in 22 minutes and 51 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #166107
cross-android_api21_arm64

00:02:47

passed #166108
cross-android_api28_arm64

00:02:46

passed #166109
cross-mingw64

00:03:10

passed #170418
fedora-autotools-x86_64

00:08:07

passed #166105
fedora-x86_64

00:05:27

manual #166112
freebsd-11 allowed to fail manual
freebsd-11-x86_64
passed #166110
win32
msys2-mingw32

00:11:14

passed #166111
win32
vs2017-x64

00:08:13

failed #170270
fedora-autotools-x86_64

00:05:56

failed #166106
fedora-autotools-x86_64

00:05:35

 
  Coverage
passed #166113
coverage

00:03:29

74.6%