Try to make etc/ci_test.sh work

[lgoettgens]

etc/ci_test.sh gets called as part of the testsuite of GAP.jl.

Already for a long time, gcov prints some errors in CI, see e.g. https://github.com/oscar-system/GAP.jl/actions/runs/10700854945/job/29665504736#step:6:468. On newer gcov version (my system uses gcc/gcov 14.2.1, while the ubuntu CI runners use 11.2.0), instead of just printing the error, this returns a non-zero exit code and thus aborts the script.
This PR contains three small changes in the hopes to fix this:

1. The gcov contained a wrong path. This is changed for JuliaInterface. Since JuliaExperimental doesn't have any c files anymore, gcov cannot give any coverage for them. So this line gets disabled.
2. The build flags of JuliaInterface now contain the needed flag to create coverage files during compilation. This would of course be nice to have only in CI cases and not always, but I don't know how to do that.
3. I added a force re-compilation of JuliaInterface before running its tests. On CI, this shouldn't change anything, but locally, I had an issue that changes to the Makefile (see previous point) didn't get picked up automatically. This forces it instead.

Alternatively, we could just remove the two lines regarding gcov from etc/ci_test.sh completely.

cc @ThomasBreuer

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 74.45%. Comparing base (e82078d) to head (faba40b).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/julia-config.jl	0.00%	6 Missing ⚠️
src/setup.jl	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1033      +/-   ##
==========================================
- Coverage   76.49%   74.45%   -2.04%     
==========================================
  Files          51       55       +4     
  Lines        4191     4534     +343     
==========================================
+ Hits         3206     3376     +170     
- Misses        985     1158     +173     

Files with missing lines	Coverage Δ
src/setup.jl	85.47% <0.00%> (+3.41%)	⬆️
src/julia-config.jl	0.00% <0.00%> (ø)

... and 4 files with indirect coverage changes

[fingolfin]

Thank you!!

[lgoettgens]

this CFLAGS variable does not get forwarded to the process that compiles JuliaInterface.

GAP.jl/src/setup.jl

Line 221 in a8674da

withenv("CFLAGS" => JULIA_CPPFLAGS,

Instead, this just uses the output of GAP.Setup.cflags() as the CFLAGS environment var. So this CFLAGS var here does not do anything.

[lgoettgens]

@ThomasBreuer noticed that gcov reports 0% coverage for all files, so something was off. As mentioned in #1033 (comment), the CFLAGS env var did not get forwarded. Instead, I now introduced JULIAINTERFACE_WITH_COVERAGE that sets the coverage flag at the appropriate location in setup.jl, and additionally adds the needed linker flag.
Locally running ]test now reports non-zero coverage in the gcov output

[fingolfin]

Thank you @lgoettgens !