odroid@odroid64:~$ sudo apt-get install gcc-4.9
odroid@odroid64:~$ sudo rm /usr/bin/gcc
odroid@odroid64:~$ sudo ln -s /usr/bin/gcc-4.9 /usr/bin/gcc
odroid@odroid64:~$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/aarch64-linux-gnu/4.9/lto-wrapper
Target: aarch64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.9.3-12ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-4.9/u
Thread model: posix
gcc version 4.9.3 (Ubuntu/Linaro 4.9.3-12ubuntu1)