tests: prefer GNU sed on BSD/OSX, BSD's sed has lame syntax
tests: prefer GNU sed on BSD/OSX, BSD's sed has lame syntax

https://blog.remibergsma.com/2012/09/18/sed-inline-editing-different-on-mac-osx/

f-droid/fdroid-server,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroid-server,fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,f-droid/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver