fix bug of check-git-abc

[nlwmode]

This project distinguishes the yosyshq/abc and berkeley-abc by .gitcommit file that checked in check-git-abc function in Makefile.

However, the second and third "elif" branches' judgment conditions are reversed. And "grep -q '$$Format:%h$$' "$(YOSYS_SRC)/abc/.gitcommit" can check that there is a .gitcommit file in yosys/abc with the text "Format:%h".

This pull request aims to ensure that the second and third "elif" conditions produce the expected compilation results for using yosyshq/abc.

[nlwmode]

This PR is to solve the issue: #4449

[widlarizer]

As others have pointed out on the linked issue, I'm confirming that the problem can't be reproduced. Furthermore, the functionality you're changing the logic for in this PR actually works for me the way I'd expect at yosys main branch commit 1288166:

emil@fridge /t/a/yosys (main)> git submodule deinit abc
Cleared directory 'abc'
Submodule 'abc' (https://github.com/YosysHQ/abc) unregistered for path 'abc'
emil@fridge /t/a/yosys (main)> make
Initialize the submodule: Run 'git submodule update --init' to set up 'abc' as a submodule.
make: *** [Makefile:770: check-git-abc] Error 1
emil@fridge /t/a/yosys (main) [2]> rm -rf abc
emil@fridge /t/a/yosys (main)> cp -r ../abc/abc-yosys-0.42/ ./abc
emil@fridge /t/a/yosys (main)> cat abc/.gitcommit
237d81397f
emil@fridge /t/a/yosys (main)> make
'abc' comes from a tarball. Continuing.

Without more context we'll probably close the PR and issue fairly soon

[widlarizer]

I strongly believe the problem is in the failure to take the git submodule status case, rather than the subsequent grep invocations. The logic is that if git doesn't know about the submodule, you look at abc/.gitcommit.

If it contains a Format string, it's a broken submodule attempt and you should get the error you're getting. This means the regex matches, grep returns 0, is negated to 1, branch is taken, you get an error.

If it contains anything else, it's probably because it literally contains a git revision hash as in the release tarballs. The regex doesn't match, grep returns 1, isn't negated, branch is taken, you don't get an error.

If it doesn't exist, you don't have either and you should be instructed to get the submodule.