Fix install path of Variorum cmake files

[tpadioleau]

Description

I would like to propose updating the path of installation of Variorum cmake files. I have tried to find the library using CMAKE_PREFIX_PATH and Variorum_ROOT but both variables could not make CMake find the library. Only specifying Variorum_DIR to the actual location of VariorumConfig.cmake worked. This is a problem for a package manager like Spack as it is relying on CMAKE_PREFIX_PATH.

My understanding is that the cmake search procedure, see https://cmake.org/cmake/help/latest/command/find_package.html#config-mode-search-procedure, cannot find VariorumConfig.cmake where it is currently installed.

With the change of the PR, I could correctly find the library with CMAKE_PREFIX_PATH and Variorum_ROOT.

Fixes #

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature/architecture support (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Build/CI update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please provide hardware architecture specs and
instructions so we can reproduce.

• Test A: Hardware architecture, machine name, example/test run
• Test B: Hardware architecture, machine name, example/test run
• ...

Checklist:

• I have run ./scripts/check-code-format.sh and confirm my code code follows the style guidelines of variorum
• I have added comments in my code
• My changes generate no new warnings (build with -DENABLE_WARNINGS=ON)
• New and existing unit tests pass with my changes

Thank you for taking the time to contribute to Variorum!

[masterleinad]

Makes sense to me.

[slabasan]

LGTM thanks!