[ci] single quote glob patterns when listing files

`git ls-files` accepts a list of patterns when listing files belonging to
the repository. If this pattern is interpreted as a glob by the shell,
it will however results in ls-files only listing the given filenames. To
avoid this issue, we need to systematically single quote the patterns
given to ls-files.

This is a difficult bug to uncover, as the shell will pass the pattern
as is if the pattern does match any files.

Note that the current gitlab-ci config does not have any issue, as there
are no .c or .h files in current working directory when these commands
are used.

Fix #60
6 jobs for ls-files-ci-fix in 3 minutes and 14 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Style
passed #55442
nix kvm
checkpatch

00:00:14

passed #55441
nix kvm
repoquality

00:00:02

passed #55443
nix kvm
style:docs

00:00:24

 
  Build
passed #55444
nix kvm
make:generic

00:00:35

passed #55446
knl
make:knl

00:02:48

passed #55445
nix kvm
make:out-of-tree

00:00:39