SOURCE_DATE_EPOCH fatal error in Arch makepkg

Hi, I am getting the following error:
```
appimagetool, continuous build (commit 7f9be69), build built on 2022-07-16 02:23:34 UTC
Desktop file: /home/dillan/Downloads/aur/openra-rv-git/src/Romanovs-Vengeance/packaging/linux/Romanovs Vengeance.appdir/openra-rv.desktop
Name: OpenRA - Romanovs Vengeance
Icon: openra-rv
Exec: openra-rv %U
Comment entry not found in desktop file
Comment: (null)
Type: Application
Categories: Game;StrategyGame;
Environmental variable ARCH used for determining architecture x86_64
Using architecture x86_64
App name for filename: OpenRA_-_Romanovs_Vengeance
/home/dillan/Downloads/aur/openra-rv-git/src/Romanovs-Vengeance/packaging/linux/Romanovs Vengeance.appdir should be packaged as /home/dillan/Downloads/aur/openra-rv-git/src/Romanovs Vengeance-3822.git.08da500-x86_64.AppImage
WARNING: AppStream upstream metadata is missing, please consider creating it
in usr/share/metainfo/openra-rv.appdata.xml
Please see https://www.freedesktop.org/software/appstream/docs/chap-Quickstart.html#sect-Quickstart-DesktopApps
for more information or use the generator at http://output.jsbin.com/qoqukof.
Generating squashfs...
Size of the embedded runtime: 189632 bytes
mksquashfs commandline: /tmp/.mount_appimaHcvpqP/usr/bin/../lib/appimagekit/mksquashfs /home/dillan/Downloads/aur/openra-rv-git/src/Romanovs-Vengeance/packaging/linux/Romanovs Vengeance.appdir /home/dillan/Downloads/aur/openra-rv-git/src/Romanovs Vengeance-3822.git.08da500-x86_64.AppImage -offset 189632 -comp gzip -root-owned -noappend -mkfs-time 0
FATAL ERROR:SOURCE_DATE_EPOCH and command line options can't be used at the same time to set timestamp(s)
Embedding ELF...
Not able to open the AppImage for writing, aborting
```

Here is the command that is running inside the makepkg script:
```
curl -s -L -O https://github.com/AppImage/AppImageKit/releases/download/continuous/appimagetool-x86_64.AppImage
chmod a+x appimagetool-x86_64.AppImage
ARCH=x86_64 ./appimagetool-x86_64.AppImage -v "${APPDIR}" "${OUTPUTDIR}/${PACKAGING_INSTALLER_NAME}-${TAG}-x86_64.AppImage"
```

I know Arch makepkg provides a SOURCE_DATE_EPOCH env variable with each run, but I am not supplying any command line options that would conflict with that. However, it looks like the `-mkfs-time 0` argument is getting hard-coded onto the command line at:
https://github.com/AppImage/AppImageKit/blob/7f9be6958ea3723d15f2e7a338e6da6e3d28baf2/src/appimagetool.c#L205-L206

Is there a way to disable this functionality, or do I need to unset the env variable in my script?