Unset GREP_OPTIONS at the start of the build. Custom grep options set in environment variables can break the build, e.g. note the line number (-n) in the following output

     ===== Processing 'gold' =====
     ===== Cloning from 2:git@github.com:t-crest/patmos-gold.git =====
    Cloning into /home/jamie/patmos/patmos-misc/gold...
    ssh: connect to host 2 port 22: Invalid argument
    fatal: The remote end hung up unexpectedly
Merge pull request #3 from t-crest/jamie_grepkill

Unset GREP_OPTIONS at the start of the build.