aportgen gcc*: set arch to x86_64 only

This covers most use cases and saves a lot of build time. Can be
changed on demand. Again, this simplifies package building as part of
the new build infrastructure effort.

pmb/aportgen/gcc.py

@@ -36,15 +36,12 @@ def generate(args, pkgname):
                          " gcc6.")
     pmb.helpers.run.user(args, ["cp", "-r", upstream, args.work + "/aportgen"])
 
-    # Architectures to build this package for
-    arches = list(pmb.config.build_device_architectures)
-    arches.remove(arch)
-
-    # Rewrite APKBUILD
+    # Rewrite APKBUILD (only building for x86_64 covers most use cases and
+    # saves a lot of build time, can be changed on demand)
     fields = {
         "pkgname": pkgname,
         "pkgdesc": "Stage2 cross-compiler for " + arch,
-        "arch": " ".join(arches),
+        "arch": "x86_64",
         "depends": "isl binutils-" + arch,
         "makedepends_build": "gcc g++ paxmark bison flex texinfo gawk zip gmp-dev mpfr-dev mpc1-dev zlib-dev",
         "makedepends_host": "linux-headers gmp-dev mpfr-dev mpc1-dev isl-dev zlib-dev musl-dev-" + arch + " binutils-" + arch,