source: PSPA/madxPSPA/cmake/ToolChains/Windows-MinGW32.cmake @ 430

# An example of how the cross compiler for mingw could look like
# Assuming you are ona Unix platform and want to build for Windows.
# You need to modify this with your own paths/binary names...

# the name of the target operating system
SET(CMAKE_SYSTEM_NAME Windows)

# which compilers to use for C and C++
SET(CMAKE_C_COMPILER i486-mingw32-gcc)
SET(CMAKE_CXX_COMPILER i486-mingw32-g++)
SET(CMAKE_Fortran_COMPILER i486-mingw32-gfortran)
SET(CMAKE_RC_COMPILER i486-mingw32-windres)

# here is the target environment located
SET(CMAKE_FIND_ROOT_PATH  /usr/i486-mingw32)

# adjust the default behaviour of the FIND_XXX() commands:
# search headers and libraries in the target environment, search 
# programs in the host environment
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)