PKG_CONFIG_LIBDIR=/usr/lib/i386-linux-gnu/pkgconfig/ \
cmake . \
-DCMAKE_SYSTEM_PROCESSOR=i386 \
--DCMAKE_Fortran_COMPILE=/some/path/to/i686-linux-gnu-gfortran \
--DGFORTRAN_EXE=/some/path/to/i686-linux-gnu-gfortran
+-DCMAKE_Fortran_COMPILER=/some/path/to/i686-linux-gnu-gfortran \
+-DGFORTRAN_EXE=/some/path/to/i686-linux-gnu-gfortran \
+-DCMAKE_Fortran_FLAGS=-m32
@endverbatim
where i686-linux-gnu-gfortran can be implemented as:
