Make more room on the semaphore build machine (#1359)

semaphore@semaphore-vm:~$ sudo rm -rf ~/.kiex ~/.phpbrew ~/.rbenv ~/.nvm ~/.kerl
Filesystem                          Size  Used Avail Use% Mounted on
udev                                1.9G     0  1.9G   0% /dev
tmpfs                               394M  7.2M  387M   2% /run
/dev/mapper/semaphore--vm--vg-root   25G   11G   15G  43% /
tmpfs                               2.0G     0  2.0G   0% /dev/shm
tmpfs                               5.0M     0  5.0M   0% /run/lock
tmpfs                               2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/sda1                           236M   71M  154M  32% /boot
tmpfs                               512M     0  512M   0% /run/shm
tmpfs                               394M     0  394M   0% /run/user/1001
/dev/sdc1                            99G   55G   40G  59% /mnt
/dev/nbd0p1                          99G   63M   99G   1% /var/lib/docker

semaphore@semaphore-vm:~$ sudo rm -rf ~/.kiex ~/.phpbrew ~/.rbenv ~/.nvm ~/.kerl ~/.sbt ~/.npm /usr/lib/jvm /opt/firefox* /opt/apache-maven* /opt/scala /usr/local/golang
Filesystem                          Size  Used Avail Use% Mounted on
udev                                1.9G     0  1.9G   0% /dev
tmpfs                               394M  7.2M  387M   2% /run
/dev/mapper/semaphore--vm--vg-root   25G  8.5G   17G  34% /
tmpfs                               2.0G     0  2.0G   0% /dev/shm
tmpfs                               5.0M     0  5.0M   0% /run/lock
tmpfs                               2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/sda1                           236M   71M  154M  32% /boot
tmpfs                               512M     0  512M   0% /run/shm
tmpfs                               394M     0  394M   0% /run/user/1001
/dev/sdc1                            99G   55G   40G  59% /mnt
/dev/nbd0p1                          99G   63M   99G   1% /var/lib/docker

.semaphore/semaphore.yml

@@ -14,7 +14,7 @@ global_job_config:
   prologue:
     commands:
       # make some room on the disk
-      - sudo rm -rf ~/.kiex ~/.phpbrew ~/.rbenv ~/.nvm ~/.kerl
+      - sudo rm -rf ~/.kiex ~/.phpbrew ~/.rbenv ~/.nvm ~/.kerl ~/.sbt ~/.npm /usr/lib/jvm /opt/firefox* /opt/apache-maven* /opt/scala /usr/local/golang
       # Semaphore mounts a copy-on-write FS as /var/lib/docker in order to provide a pre-loaded cache of
       # some images. However, the cache is not useful to us and the copy-on-write FS is a big problem given
       # how much we churn docker containers during the build.  Disable it.