Add support for NVIDIA nvc++ compiler

[cgleggett]

This Pull request:

Adds support for NVIDIA's nvc++ compiler

Changes or fixes:

• check if at least ver 24.11 of nvc++ compiler is being used
• when building cling, nvc++ uses a different syntax than gcc to extract the system include header locations. Instead of -xc++ -E -v, and then a bunch of sed parsing, it uses the -drygccinc flag to produce a colon separated list of paths.

This allows clean compilation on ARM (NVIDIA Grace) CPUs.

[github-actions]

Test Results

    18 files      18 suites   4d 15h 23m 21s ⏱️
 2 683 tests  2 683 ✅ 0 💤 0 ❌
46 430 runs  46 430 ✅ 0 💤 0 ❌

Results for commit f41386a.

[vgvassilev]

Have you tried to run the test suite for ROOT with this pull request and nvcc? My worry is that we have to execute cuda code in the interpreter through clang and some changes in the interpreter's cmake files seem to go towards getting the nvcc runtime somehow in cling.

[vgvassilev]

Don't we need a check here for NVHPC too?

[hahnjo]

As far as I understand this condition filters out supported compilers. As NVHPC is only partially supported, it must enter this condition - note the NOT in front.

[hahnjo]

@cgleggett so this means the most recent nvc++ is "fixed enough" to build a working LLVM and ROOT? So all dictionaries build and basic operation works, ie running some of the basic tutorials?

[cgleggett]

what is the recommended way to test a build? I was able to do I/O and read/write root files, but that obviously doesn't cover everything.

[pcanal]

If you would like to run the full test suite, you can configure with:

cmake -Droottest="ON" -Dtesting="ON" .

and run ctest -j something (it takes a while :) ).

You can also start without the -Droottest=ON to get the "unit" test and tutorials to run.