[CMake] how to build two libraries from same sources but with different defines?

[Igor Karatayev]

Hello.

I am building my library for two different processors arm7 and arm9.
devkitArm requeres ARM7 or ARM9 macroses should be defined when
building for any processor. I tried to write

include_directories(./)

set(SOURCES
   src/library.cpp
   )

   add_definitions(-DARM7)
   add_library(sandbox-arm7 ${SOURCES})
   remove_definitions(-DARM7)
   add_definitions(-DARM9)
   add_library(sandbox-arm9 ${SOURCES})
   remove_definitions(-DARM9)

but it does not work as expected.