Add support for MUSL libc

[sodomon2]

Adding musl libc support would be nice, as I tried to build it on alpine linux (musl not glibc) and there are too many bugs.

[briaguya-ai]

if you could provide details on what the bugs are that would be helpful. i'm all for making the codebase more portable, having the issues documented would help a ton!

[sodomon2]

The first error I get is this, I don't know if this is in all musl based systems or if it only happens in Alpine (the distro I use).

$ cmake ..
-- The C compiler identification is GNU 13.2.1
-- The CXX compiler identification is GNU 13.2.1
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at CMake/Utils.cmake:238 (message):
  Could not detect lsb_release executable, can not gather required
  information
Call Stack (most recent call first):
  CMakeLists.txt:65 (get_linux_lsb_release_information)


-- Configuring incomplete, errors occurred!

I avoid the error by eliminating the check

if(CMAKE_SYSTEM_NAME MATCHES "Linux")
    get_linux_lsb_release_information()
    message(STATUS "Linux ${LSB_RELEASE_ID_SHORT} ${LSB_RELEASE_VERSION_SHORT} ${LSB_RELEASE_CODENAME_SHORT}")
else()
    message(STATUS ${CMAKE_SYSTEM_NAME})
endif()

the fix is as follows

if(CMAKE_SYSTEM_NAME MATCHES "Linux")
    message(STATUS ${CMAKE_SYSTEM_NAME})
endif()

[sodomon2]

After doing all that, the following error has to do with OpenGL

-- Linux
-- Linking against dependent libraries statically
-- Using the multi-header code from /home/sodomon/Shipwright/libultraship/extern/nlohmann-json/include/
Searching for Boost installation
Boost found in /usr/include
convert: unable to open image 'soh/macosx/sohIcon.png': No such file or directory @ error/blob.c/OpenBlob/3572.
convert: no images defined `/home/sodomon/Shipwright/build/sohIcon.png' @ error/convert.c/ConvertImageCommand/3362.
-- Configuring done (1.6s)
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
OPENGL_glx_LIBRARY (ADVANCED)
    linked by target "ImGui" in directory /home/sodomon/Shipwright/libultraship/extern
OPENGL_opengl_LIBRARY (ADVANCED)
    linked by target "ImGui" in directory /home/sodomon/Shipwright/libultraship/extern

I also fix it by patching the CMakeFile replacing OPENGL_glx_LIBRARY and OPENGL_opengl_LIBRARY by OPENGL_GL_LIBRARY.