Fixed installation; other projects can now find module files from fortran-support

What is the bug

Any projects dependent on fortran-support are not able to find the associated module files of when the fortran-support is installed in the system

How do you fix it

CMAKE_INSTALL_PREFIX was not used to define INSTALL_INTERFACE. I corrected it now.

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

• Test coverage does not decrease
• Reviewed by a maintainer
• Incorporate review suggestions
• 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
• Remember to edit the commit message and select the proper changelog category (feature/bugfix/other)

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

src/CMakeLists.txt

@@ -107,7 +107,7 @@ target_include_directories(
   PUBLIC
     # Path to the Fortran modules:
     $<BUILD_INTERFACE:$<$<COMPILE_LANGUAGE:Fortran>:${Fortran_MODULE_DIRECTORY}>>
-    $<INSTALL_INTERFACE:$<$<COMPILE_LANGUAGE:Fortran>:${CMAKE_INSTALL_INCLUDEDIR}>>
+    $<INSTALL_INTERFACE:$<$<COMPILE_LANGUAGE:Fortran>:${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR}>>
   INTERFACE
     # Path to the internal C/C++ headers (for testing): Requires CMake 3.15+ for
     # multiple compile languages