Fix CMake install path not taking environmental path

What is the bug

CMake install path needs to be defined explicitly and thus hard to cooperate with upperlayer repositories. Also see libfortran-support!103 (merged)

How do you fix it

Use $<INSTALL_PREFIX> instead of ${CMAKE_INSTALL_PREFIX}

How urgent is the bugfix

• I need it as soon as possible
• I can wait for a couple of days
• None of my current codes is directly affected

Mandatory steps before review

• Gitlab CI passes (Hint: use make format for linting)
• Bugfix is covered by additional unit tests
• Mark the merge request as ready by removing Draft:

Mandatory steps before merge

• Reviewed by a maintainer
• Incorporate review suggestions
• Remember to edit the commit message and select the proper changelog category (feature/bugfix/other)
• Prior to merging, please remove any boilerplate from the MR description, retaining only the What is the bug and How do you fix it section to maintain

You are not supposed to merge this request by yourself, the maintainers of libiconmath take care of this action!

added bug ready for review labels

requested review from @k202170

assigned to @b382190

I still have doubts regarding the necessity of this change. I was trying to implement the exact change you did here myself this morning. Before that, I was checking how it worked in fortran-support. I found it surprising that the change made in fortran-support did not change anything in fortran-support-target.cmake as Sergey suggested it would. As I found, it still has:

set_target_properties(fortran-support::fortran-support PROPERTIES
  INTERFACE_INCLUDE_DIRECTORIES "\$<\$<COMPILE_LANGUAGE:Fortran>:/path/to/libfortran-support/include>"
)

Could you check it yourself? Please also see if there is any change in the file src/cmake_install.cmake. For me, there is none, and it uses CMAKE_INSTALL_PREFIX to install the library.

marked the checklist item Gitlab CI passes (Hint: use make format for linting) as completed

approved this merge request

resolved all threads

marked the checklist item Reviewed by a maintainer as completed

marked the checklist item Remember to edit the commit message and select the proper changelog category (feature/bugfix/other) as completed

marked the checklist item Prior to merging, please remove any boilerplate from the MR description, retaining only the What is the bug and How do you fix it section to maintain as completed

merged

mentioned in commit 3c2365d9