Fix linux distribution detection: "pacman" is also a very popular game.

2 jobs from linux_distrib in 3 minutes and 40 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #5414
img

03:40

failed #5129
img

05:48

 
Name Stage Failure
failed
img Test
make[2]: *** [all] Error 2
Makefile:848: recipe for target 'all' failed
make[2]: Leaving directory '/builds/jferard/redox/prefix/binutils-build'
make[1]: *** [/builds/jferard/redox/prefix/binutils-install] Error 2
mk/prefix.mk:22: recipe for target '/builds/jferard/redox/prefix/binutils-install' failed
make[1]: Leaving directory '/builds/jferard/redox'
make: *** [ci-img] Error 2
Makefile:63: recipe for target 'ci-img' failed
ERROR: Job failed: exit code 1