Source devtoolset in CentOS Dockerfile (#445)
Source devtoolset in CentOS Dockerfile (#445)

It looks like the argument passing from the "scl enable" command doesn't
preserve quotes very well. It isn't the recommended practice for SCLs,
but we can source the enablement script instead. I've seen this pattern
used in RPMs in the past, so it should be stable enough for this.
ros2/ci,ros2/ci,ros2/ci