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
It should be unpacket it in ~/vu/opt/ on you build environment because the envARM.sh uses this path

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

Cross Compiling with DVBCSA, then copy these files to your build environment:

• The header file dvbcsa.h needs to go here:
  ~/vu/opt/toolchains/stbgcc-8.3-0.4/arm-unknown-linux-gnueabihf/include/c++/8.3.0/dvbcsa/dvbcsa.h
  
• Find on the receiver /usr/lib/libdvbcsa.so.1.0.1 and just copy and rename it to:
  ~/vu/opt/toolchains/stbgcc-8.3-0.4/arm-unknown-linux-gnueabihf/lib/libdvbcsa.so
  
• You can install libdvbcsa package in (OpenATV or Teamblue) with:
  opkg install libdvbcsa
  
  

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