change CI CMake build to use Open Watcom toolchain

[jmalak]

add __export modifier if DLL is requested to properly generate import library zlib.lib for OS/2
add CMake cross-compilation build by Open Watcom for 16/32-bit DOS and OS2, 32-bit Windows and 32-bit Linux

[madler]

Have you tested all of those builds you are proposing to add to cmake.yml?

[jmalak]

I tested build only.
For Windows it is build static library and DLL and link samples with DLL and run samples.
For Linux it is build static library only and link samples with static library and run samples.
For DOS it is build only static library and link samples, not tested.
For OS/2 it is build DLL and link samples with DLL, not tested.

You can check build and test result here

[nmoinvaz]

This step shouldn't need a separate version for watcom.

[jmalak]

I don't want to change anything for other compilers because I have no experiencies with them and cmake.
matrix.compiler is as class for watcom instead of for others. Also cmake support Watcom compilers cross-compilation without need of special cmake configuration scripts. it is control directly by CMAKE_SYSTEM_NAME and CMAKE_SYSTEM_PROCESSOR macros. And also reference to current directory for output files is not good solution for Watcom because some intermediate files created by Watcom overwrite zlib source files. That during testing destroys sources and you cannot repeate steps. I did it this simple way that matrix.compiler is used to switch to watcom logic and not control Watcom version etc. It can be changed to any other variable, but we need to know if WATCOM toolchain or others somehow to switch between two modes.

!!!! Important change is that you must not setup environment CC: ${{ matrix.compiler }} for Watcom, which is main reason to do it this way for watcom (you must not setup CC: variable any way) !!!!!

[jmalak]

I separated CI CMake build change from OS/2 build fix that here is only CI CMake related changes

[jmalak]

NOTE for CMake use with watcom:

• watcom must be used with -G "Watcom WMake" because it setup WATCOM stuff in CMake
• watcom mode in CMake doesn't use POSIX CC mechanism, therefore you cannot use CC environment variable

[jmalak]

I submit new #958 PR with OS/2 DLLbuild fix that this PR is only for CI CMake build changes

[jmalak]

I little reworked CI CMake actions script by using if conditions to follow existing workflow without specific actions for Watcom
Now it is fully controlled by if conditions

[jmalak]

Pre-requisity for this change is PR "correct Open Watcom OS/2 build #958"