Improve OpenMP configuration

What is the bug

OpenMP_C is not used and cannot be found with Mac clang, which cause a compile trouble. This MR solves #25 (closed).

How do you fix it

Only find OpenMP and link for Fortran. Along the way, one bug for insert_dimension is also fixed with this MR.

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

@@ -21,11 +21,6 @@ test_big_endian(HAVE_BIG_ENDIAN)
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/config.h.in
                ${CMAKE_CURRENT_BINARY_DIR}/config.h)
 
-if(FS_ENABLE_OMP)
-  find_package(OpenMP REQUIRED)
-  set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} ${OpenMP_Fortran_FLAGS}")
-endif()
-
 add_library(
   fortran-support
   ${CMAKE_CURRENT_BINARY_DIR}/config.h
@@ -90,6 +85,11 @@ if(FS_ENABLE_SINGLE_PRECISION)
   target_compile_definitions(fortran-support PRIVATE __SINGLE_PRECISION)
 endif()
 
+if(FS_ENABLE_OMP)
+  find_package(OpenMP COMPONENTS Fortran REQUIRED)
+  target_link_libraries(fortran-support PUBLIC OpenMP::OpenMP_Fortran)
+endif()
+
 include("${PROJECT_SOURCE_DIR}/cmake/check_macro.cmake")
 check_macro_defined(HAS_OPENACC_MACRO _OPENACC QUIET)
 if(FS_ENABLE_OPENACC)