build/travis: fix GOPATH for make install
build/travis: fix GOPATH for make install

Travis defines $GOPATH like this:

    export GOPATH=$HOME/gopath:

(notice the colon?)

From the official Go documentation:
"The GOPATH environment variable specifies the location of your
workspace."

As such, it shall point to one directory and does not act like $PATH.
Hence, workaround that weird GOPATH definition from Travis for the
dependencies installation.

DevMine/repotool