First up, download the File Geodatabase API from here. You’ll need create an ESRI Global account and agree to the API’s EULA. Once the API’s tarball is downloaded, extract it and keep track of where you put it. Next up, download GDAL’s PKGBUILD, a patch, and changelog from here. All three files need to be in the same directory. Next, edit the PKGBUILD to look for the API. Personally I put the API in /opt so I added:
and then ran mkgpkg. Once GDAL finished compiling pacman -U upgraded gdal. Now I can go into QGIS, click Add Vector, click the Directory radio button, and select File GDB in the file type drop down. Easy peasy.