CachedCMakePackage: remove hardcoded hipcc

[white238]

This was in multiple packages in a place that had no impact due to cache variables being immutable in CMake. It got moved into a common location but higher in the generated CMake initial cache.

This should not be hardcoded due to wanting to use crayCC, amdclang++, or hipcc as your ROCM compiler.

[adrienbernede]

@white238 This is causing issues (with mixed %gcc +rocm targets) that were not detected at testing time because changes in CachedCMakePackage are not interpreted as changes in the package themselves.

Now, looking at the history, I think you might have missed a tiny detail about the way it used to be:
E.g, in RAJA it used to look like this:

            entries.insert(0, cmake_cache_path("CMAKE_CXX_COMPILER", spec["hip"].hipcc))

Meaning the CMAKE_CXX_COMPILER was inserted at the top of the file!

@becker33 @trws for reference.

[adrienbernede]

I found that in the commit at the root of my PR:

spack/var/spack/repos/builtin/packages/raja/package.py

Line 115 in 4b61870

entries.insert(0, cmake_cache_path("CMAKE_CXX_COMPILER", spec["hip"].hipcc))

[white238]

Yea @becker33 and I discussed this directly yesterday. When I made this PR i missread that line as after it was defined (too many moving parts at a time, my bad). It was definitely having an impact on the packages that had it. @becker33 is addressing the pipeline fallout in #43638