CMakeLists: fixed default build type, added option for static build

[Honza-R]

Small improvements in CMakeLists

Issue: When CMAKE_BUILD_TYPE was not provided by the user (the variable was empty), cmake defaulted to a debug build. As a result, the default compilation run without any options (and that's what most users will do) yields a binary with lower performance.

Solution: The default value is set depending on ENABLE_COVERAGE which correctly defaults to OFF. Therefore, in no options are set by user, the build type is set to "Release". Additionally, if both options are set, conflict between CMAKE_BUILD_TYPE=Release and ENABLE_COVERAGE=ON is checked and yields an error.

Additional feature: I've added a new option STATIC_BUILD for building a static binaries. The default is OFF, and the script behaves the same as before. The static compilation works well with gfortran/OpenBlas but fails with Intel/MKL.

Status

• Ready for merge

[codecov-commenter]

Codecov Report

Merging #35 (de67917) into main (47634e0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #35   +/-   ##
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  Coverage   68.23%   68.23%           
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  Files         330      330           
  Lines       71589    71589           
=======================================
  Hits        48852    48852           
  Misses      22737    22737           

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[godotalgorithm]

I generally welcome changes to MOPAC's CMake build system to improve user friendliness that don't break any existing use cases.

However, I'm trying to comply with the latest CMake standards of target-specific options rather than global options, so I've made some changes to your PR. I'm using multiple target_link_options commands instead of modifying CMAKE_EXE_LINKER_FLAGS. The CMAKE_FIND_LIBRARY_SUFFIXES change is in a gray area here - it is a global option, but I am not aware of an equivalent target option and it seems to be reset between projects anyways to avoid problems.

This should function exactly like your original PR, and if it doesn't please open an Issue or file another PR as needed.