[core] Use automatic build tree detection for all resource directories

[guitargeek]

This follows up on a5b1ed9, using the mechanism to automatically detect if we are in the build tree or install tree also for the other resource directories (so far it was only implemented for the include directory as a first test).

Several fallbacks and hacks can be removed because of this change, like the ROOTIGNOREPREFIX variable that was needed to run ROOT in the build tree for the tests.

This change also makes ROOT completely independent of the ROOTSYS environment variable and therefore unblocks #20006.

If one wants to check that all the resource directories (inlcuding RootSys()) are correct, one can use this check:

void checkdirs() {

    std::cout << "Bin       : " << gROOT->GetBinDir() << std::endl;
    std::cout << "Data      : " << gROOT->GetDataDir() << std::endl;
    std::cout << "Doc       : " << gROOT->GetDocDir() << std::endl;
    std::cout << "Etc       : " << gROOT->GetEtcDir() << std::endl;
    std::cout << "Icon      : " << gROOT->GetIconPath() << std::endl;
    std::cout << "Include   : " << gROOT->GetIncludeDir() << std::endl;
    std::cout << "Lib       : " << gROOT->GetLibDir() << std::endl;
    std::cout << "Macro     : " << gROOT->GetMacroDir() << std::endl;
    std::cout << "RootSys   : " << gROOT->GetRootSys() << std::endl;
    std::cout << "SharedLib : " << gROOT->GetSharedLibDir() << std::endl;
    std::cout << "Source    : " << gROOT->GetSourceDir() << std::endl;
    std::cout << "TTFFont   : " << gROOT->GetTTFFontDir() << std::endl;
    std::cout << "Tutorial  : " << gROOT->GetTutorialDir() << std::endl;
}

[github-actions]

Test Results

    21 files      21 suites   3d 3h 17m 35s ⏱️
 3 830 tests  3 576 ✅   1 💤 253 ❌
73 059 runs  72 373 ✅ 433 💤 253 ❌

For more details on these failures, see this check.

Results for commit 180ebb0.

♻️ This comment has been updated with latest results.

[vepadulano]

https://github.com/root-project/root/actions/runs/21481040637/job/61888781030?pr=21018#step:7:18 This error probably means that ROOT cannot even start and the process segfaults.

[guitargeek]

https://github.com/root-project/root/actions/runs/21481040637/job/61888781030?pr=21018#step:7:18 This error probably means that ROOT cannot even start and the process segfaults.

This is fixed by that PR:

• [build] Use CMAKE_INSTALL_<dir> variables consistently in setup.py #21075