tests: Fix ASAN build on macOS

[neverpanic]

Description

On macOS, the variable for library preloading is DYLD_INSERT_LIBRARIES, not LD_PRELOAD. Adjust the CHECKER env variable to use that on macOS machines.

Change fake_dlclose to a library rather than a shared module. This doesn't make a difference on Linux, but on macOS, dyld(1) refuses to insert a shared module into a processes address space using DYLD_INSERT_LIBRARIES, but allows a library in the same place.

Checklist

• Code modified for feature
• Test suite updated with functionality tests
• Test suite updated with negative tests
• Documentation updated

Reviewer's checklist:

• Any issues marked for closing are addressed
• There is a test suite reasonably covering new functionality or modifications
• This feature/change has adequate documentation added
• Code conform to coding style that today cannot yet be enforced via the check style test
• Commits have short titles and sensible commit messages
• Coverity Scan has run if needed (code PR) and no new defects were found

[Jakuje]

thank you! Looks good!

[simo5]

Thanks Clemens!