gio-tool: Print Unix mount point information where available

This is useful when debugging glib#1643, and might be considered to be
generically interesting information.

Signed-off-by: Simon McVittie <smcv@collabora.com>
9 jobs for gio-tool-mounts in 19 minutes and 49 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #183265
cross-android_api21_arm64

00:02:49

passed #183266
cross-android_api28_arm64

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passed #183267
cross-mingw64

00:03:02

passed #183264
fedora-autotools-x86_64

00:07:36

passed #184059
fedora-x86_64

00:05:47

passed #183268
win32
msys2-mingw32

00:11:26

passed #183269
win32
vs2017-x64

00:08:00

failed #183263
fedora-x86_64

00:04:13

 
  Coverage
passed #183270
coverage

00:02:34

75.5%