core: Arch: define supported arches as a set (MR 2474)

Rather than a list which we later convert to a set.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>

pmb/core/arch.py

@@ -80,9 +80,7 @@ class Arch(enum.Enum):
         specify architectures supported by Alpine here. For cross-compiling,
         we need to generate the "musl-$ARCH" and "gcc-$ARCH" packages (use
         "pmbootstrap aportgen musl-armhf" etc.)."""
-        # FIXME: cache?
-        return set(
-            [
+        return {
             Arch.armhf,
             Arch.armv7,
             Arch.aarch64,
@@ -91,8 +89,7 @@ class Arch(enum.Enum):
             Arch.riscv64,
             Arch.ppc64le,
             Arch.native(),
-            ]
-        )
+        }
 
     # FIXME: we should use pmaports.cfg "supported_arches" instead
     @staticmethod