add #define SDL_DISABLE_WINDOWS_IME

[ 50%] Linking C shared library SDL2.dll
LINK: command "C:\PROGRA2\MICROS1\2019\COMMUN1\VC\Tools\MSVC\14291.301\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\SDL2.dir\objects1.rsp /out:SDL2.dll /implib:SDL2.lib /pdb:C:\sdl2\build\SDL2.pdb /dll /version:2.0 /NODEFAULTLIB /machine:x64 /INCREMENTAL:NO user32.lib gdi32.lib winmm.lib imm32.lib ole32.lib oleaut32.lib version.lib uuid.lib advapi32.lib setupapi.lib shell32.lib dinput8.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:SDL2.dll.manifest" failed (exit code 1120) with the following output:
Creating library SDL2.lib and object SDL2.exp
SDL_windowskeyboard.c.obj : error LNK2019: unresolved external symbol IME_ClearComposition referenced in function WIN_ClearComposition
SDL_windowskeyboard.c.obj : error LNK2019: unresolved external symbol IME_IsTextInputShown referenced in function WIN_IsTextInputShown
SDL2.dll : fatal error LNK1120: 2 unresolved externals
NMAKE : fatal error U1077: '"C:\Program Files\CMake\bin\cmake.exe"' : return code '0xffffffff'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.29.30133\bin\HostX64\x64\nmake.exe"' : return code '0x2'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.29.30133\bin\HostX64\x64\nmake.exe"' : return code '0x2'
Stop.
Command exited with code 2