removed os2 support & support for building SDL with watcom.

cmake/sdlchecks.cmake

@@ -364,7 +364,7 @@ macro(CheckLibSampleRate)
           get_property(_samplerate_type TARGET SampleRate::samplerate PROPERTY TYPE)
           if(_samplerate_type STREQUAL "SHARED_LIBRARY")
             set(HAVE_LIBSAMPLERATE_SHARED TRUE)
-            if(WIN32 OR OS2)
+            if(WIN32)
               set(SDL_LIBSAMPLERATE_DYNAMIC "\"$<TARGET_FILE_NAME:SampleRate::samplerate>\"")
             else()
               set(SDL_LIBSAMPLERATE_DYNAMIC "\"$<TARGET_SONAME_FILE_NAME:SampleRate::samplerate>\"")
@@ -1172,8 +1172,6 @@ macro(CheckHIDAPI)
           set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${PKG_LIBUSB_CFLAGS}")
           if(HIDAPI_ONLY_LIBUSB)
             list(APPEND EXTRA_LIBS ${PKG_LIBUSB_LIBRARIES})
-          elseif(OS2)
-            set(SDL_LIBUSB_DYNAMIC "\"usb100.dll\"")
           else()
             # libusb is loaded dynamically, so don't add it to EXTRA_LIBS
             FindLibraryAndSONAME("usb-1.0" LIBDIRS ${PKG_LIBUSB_LIBRARY_DIRS})