fix: install antergos-next-keyring during basestrap, remove artix-release from target

- Add antergos-next-keyring to basestrap install list so keyring files
  are available in the target early (uses host keyring which already
  trusts the Antergos key)
- Add antergos-next to keyrings list so pacman-key --populate imports
  the Antergos key into the target's keychain
- try_remove artix-release so antergos-release doesn't conflict when
  packages module runs later (replaces= PKGBUILD fix also pushed, but
  this works regardless of rebuild)
- Fix remove() method in basestrap main.py: was missing --root <target>,
  causing removals to operate on the HOST instead of the target

iso-profiles/antergos/live-overlay/usr/lib/calamares/modules/basestrap/main.py

@@ -370,7 +370,11 @@ class PMPacman(PackageManager):
 
     def remove(self, pkgs):
         self.reset_progress()
-        self.run_pacman(["pacman", "-Rs", "--noconfirm"] + pkgs, True)
+        install_root = libcalamares.globalstorage.value("rootMountPoint")
+        command = ["pacman"]
+        command.extend(self.get_optargs(install_root))
+        command += ["-Rs", "--noconfirm"] + pkgs
+        self.run_pacman(command, True)
 
     def get_optargs(self, rootdir):
         cachedir = join(rootdir, "var/cache/pacman/pkg")