https://gcc.gnu.org/svn.html

https://gcc.gnu.org/wiki/InstallingGCC

https://wiki.debian.org/ArmHardFloatPort#Minimum_CPU_.26_FPU

https://www.raspberrypi.org/forums/viewtopic.php?f=33&t=146222

# eg. to install GCC 4.8.5
$ svn co svn://gcc.gnu.org/svn/gcc/branches/gcc-4_8_5_release gcc-4.8.5
$ cd gcc-4.8.5
$ ./contrib/download_prerequisites
$ cd ..
$ mkdir objdir
$ cd objdir

# it is recommended to configure at the other directory
$ $PWD/../gcc-4.8.5/configure --prefix=$HOME/GCC-4.8.5
# "--enable-languages=c,c++" is not used
$ make
$ make install