Merge branch 'issue-68-use-gcc-o1' into 'master'

Fix #68: Use -O1 when compiling with gcc now

Closes #68

See merge request !45
2 jobs for master in 18 minutes and 34 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #1537
linux
linux-runner

00:18:33

passed #1538
osx
osx-runner

00:09:21