CI: test_ui: get arches from pmaports.cfg (MR 3205)

Don't assume that each branch has all arches that pmbootstrap supports,
instead add them to pmaports.cfg and read them from there. This should
allow the test to pass on v22.06.

.ci/testcases/test_ui.py

@@ -15,7 +15,9 @@ def test_aports_ui(args):
     """
     Raise an error if package in _pmb_recommends is not found
     """
-    for arch in pmb.config.build_device_architectures:
+    pmaports_cfg = pmb.config.pmaports.read_config(args)
+
+    for arch in pmaports_cfg["supported_arches"].split(","):
         for path in glob.iglob(args.aports + "/main/postmarketos-ui-*/APKBUILD"):
             apkbuild = pmb.parse.apkbuild(path)
             # Skip if arch isn't enabled

pmaports.cfg

@@ -8,3 +8,4 @@ supported_firewall=nftables
 supported_base_nofde=True
 supported_install_boot_label=pmOS_i_boot
 supported_mkinitfs_without_flavors=True
+supported_arches=x86_64,x86,aarch64,armv7,armhf