Here is an Cross Compiling Toolchain, I use for Vu+/GigaBlue Receivers (Broadcom CPU) it has MIPS and ARM cross-compiler:
https://github.com/Broadcom/stbgcc-6.3/releases
https://github.com/Broadcom/stbgcc-8.3/releases

If you like to run it on an Enigma2 box (With the correct toolchain), use:
source envARM.sh -> Only once, to enable build environment for ARM Broadcom cross-compiler
source envMIPS.sh -> Only once, to enable build environment for MIPS Broadcom cross-compiler
source envMIPSEL.sh -> Only once, to enable build environment for MIPSEL Broadcom cross-compiler
make ENIGMA=yes -> Normal build with Enigma support
make debug ENIGMA=yes -> Debug build with Enigma support

For Cross Compiling if there is no specific toolchain, here are some tips you can try (I did not try this myself):

• get the sys root like headers and libraries for your device and copy it to dir
  export INCLUDES=--sysroot=dir
  
• for pointing to a different compiler for your device
  export CXXPREFIX=arm-linux-gnueabihf-
export CXXSUFFIX=
  
• To buils just run (Or some other build you like)
  make debug