config: switch to new binary package repository (!1835)

This change has been in the works for about a year now. We have a new
binary repository, that is completely automated and always online.
Powered by builds.sr.ht and our very own build.postmarketos.org code.
The days of yours truly manually triggering to build and upload the
binary package repository at home are finally over! Also this will pave
the way to have multiple branches, and to base on Alpine stable.

Related: https://postmarketos.org/blog/2019/01/16/600-days-of-postmarketOS/#new-srht-based-binary-repository
Related: https://postmarketos.org/blog/2019/06/23/two-years/#sourcehut-srht
Related: https://gitlab.com/postmarketOS/build.postmarketos.org

pmb/config/__init__.py

@@ -77,7 +77,7 @@ defaults = {
     "keymap": "",
     "log": "$WORK/log.txt",
     "mirror_alpine": "http://dl-cdn.alpinelinux.org/alpine/",
-    "mirrors_postmarketos": ["http://postmarketos.brixit.nl"],
+    "mirrors_postmarketos": ["http://postmarketos1.brixit.nl/postmarketos/master"],
     "nonfree_firmware": True,
     "nonfree_userland": False,
     "port_distccd": "33632",

pmb/data/keys/README

@@ -6,4 +6,4 @@ Sources for the keys (must be identical, there's a testcase that verifies this):
 	alpine-keys package
 
 In addition, this key holds keys for the official postmarketOS repository:
-	https://github.com/postmarketOS/pmbootstrap/issues/871
+	https://build.postmarketos.org