gutils: Add g_get_os_info()

Add a new function that gets OS information for /etc/os-release.
12 jobs for g-os-info in 46 minutes and 55 seconds (queued for 3 minutes and 24 seconds)
Status Job ID Name Coverage
  Build
passed #407308
cross-android_api21_arm64

00:02:40

passed #407309
cross-android_api28_arm64

00:02:44

passed #407310
cross-mingw64

00:03:08

passed #407306
debian-stable-x86_64

00:04:17

passed #408292
fedora-x86_64

00:04:18

passed #408293
G_DISABLE_ASSERT

00:03:06

passed #407311
win32
msys2-mingw32

00:13:30

passed #407312
win32
vs2017-x64

00:09:28

failed #407305
fedora-x86_64

00:10:28

failed #407307
G_DISABLE_ASSERT

00:04:13

 
  Coverage
passed #407313
coverage

00:01:40

77.9%
 
  Analysis
passed #407314
scan-build

00:13:38