This line is the most important one from the output:
error: X11 library is missing: install XQuartz from xquartz.macosforge.org
You can install XQuartz, or (probably easier), install the slightly older binary version of Rcmdr. To do the latter, when it says "There are binary versions available but the source versions are later. Do you want to install from sources the package which needs compilation?" choose no.
Eventually the binary version on CRAN will catch up to the source version (when there's an update to a package, it takes some time to build the binaries).