If you encounter an error during the build process that resembles one of the following:
ERROR: (#/#) [CC] tmp/cmd/command.o /usr/bin/g++-5.0 -c -std=c++11 -pthread -fPIC -I/home/user/mrtrix3/eigen -Wall -O2 -DNDEBUG -Isrc -Icmd -I./lib -Icmd cmd/command.cpp -o release/cmd/command.o failed with output g++-4.8: internal compiler error: Killed (program cc1plus) Please submit a full bug report, with preprocessed source if appropriate. See for instructions.
ERROR: ( 9/498) [CC] tmp/src/directory/header.o g++ -c -std=c++11 -pthread -fPIC -DMRTRIX_WORD64 -DMRTRIX_TIFF_SUPPORT -isystem /usr/include/x86_64-linux-gnu -DEIGEN_FFTW_DEFAULT -Wall -O3 -DNDEBUG -Isrc -I./core -Icmd -isystem /usr/include/eigen3 -DEIGEN_DONT_PARALLELIZE src/directory/header.cpp -o tmp/src/registration/transform/rigid.o_ failed with output cc1plus: out of memory allocating 4064 bytes after a total of 35667968 bytes
This is most typically caused by the compiler running out of RAM. This can be solved either through installing more RAM into your system, or by restricting the number of threads to be used during compilation:
$ NUMBER_OF_PROCESSORS=1 ./build