build: Make lint-locale-dependence.sh work with BSD grep (avoid empty subexpressions) #13720

Make lint-locale-dependence.sh work with BSD grep by avoiding empty subexpressions.

macOS High Sierra:

$ grep --version
grep (BSD grep) 2.5.1-FreeBSD
$ echo foo | grep -E '^foo(_r|_s)?$'
foo
$ echo foo | grep -E '^foo(|_r|_s)$'
grep: empty (sub)expression

Ubuntu 18.04 LTS:

$ grep --version
grep (GNU grep) 3.1
$ echo foo | grep -E '^foo(_r|_s)?$'
foo
$ echo foo | grep -E '^foo(|_r|_s)$'
foo

Reported by @masonicboom in #13708 (review). Thanks!

utACK 5a3eefc4 how much work would it be to make the scripts fully compatible with BSD grep? Would be nice to remove the gnu grep requirement.

There's another empty subexpression in lint-shell-locale.sh, line 18

@Empact Fixed the GNU:Ism in lint-shell-locale.sh. Do you know of any other incompatibility with BSD grep? I've now added a linter that will help us avoid introducing GNU:isms in our shell scripts :-)

Please re-review!

Thanks for doing this but... sigh more shell-lowest-common-denominator-porting I wish we just bit the bullet ported this stuff to Python so that it's, by definition, not dependent on external tools.

As an alternative to the linter here, I set up running the linter checks on Mac via Travis, #13728.

<!--e57a25ab6845829454e8d69fc972939a-->Note to reviewers: This pull request conflicts with the following ones:

• #13728 (Scripts and tools: Run the CI lint stage on mac and linux both by Empact)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

I prefer @Empact:s solution in #13728 which runs the linter chers on Mac via Travis

Closing this PR since it won't be relevant when #13728 has been merged.