Fix arch build

For some reason libffi is not installed even though make needs it

Signed-off-by: Dorian Stoll <dorian.stoll@tmsp.io>

.github/workflows/arch.yml

@@ -20,7 +20,7 @@ jobs:
     - name: Install build dependencies
       run: |
         # Install makepkg deps
-        pacman -Sy --noconfirm sudo binutils fakeroot grep base-devel git sbsigntools
+        pacman -Sy --noconfirm sudo binutils fakeroot grep base-devel git sbsigntools libffi
 
     - name: Setup secureboot certificate
       env: