nsis: StrCmp is a installation time instruction !

so use !if to not include files

install/WinInstaller.nsi

@@ -93,16 +93,16 @@ Section "Grafx2" SecProgram
   File "..\src-${VERSION}.tgz"
   SetOutPath "$INSTDIR\bin"
   File ..\bin\grafx2-${API}.exe
-  StrCmp ${API} "sdl" 0 nosdl
+  !if ${API} == "sdl"
     File ..\bin\SDL_image.dll
     File ..\bin\SDL.dll
     File ..\bin\SDL_ttf.dll
-  nosdl:
     File ..\bin\${FREETYPEDLL}
     File ..\bin\${JPEGDLL}
+    File ..\bin\${TIFFDLL}
+  !endif
   File ..\bin\zlib1.dll
   File ..\bin\${PNGDLL}
-  File ..\bin\${TIFFDLL}
   SetOutPath "$INSTDIR\share\grafx2"
   File ..\share\grafx2\gfx2.gif
   File ..\share\grafx2\gfx2def.ini