phase2: signpack: fix sha256sums signatures of apk packages.adb index

Currently the sha256sum verification of apk's packages.adb index
fails as the file is modified with `apk adbsign`, but we currently don't
send the sha256sums file to the master, thus it can't be fixed during
signing.

So lets pack sha256sums files and ship them to master for proper
signing.

Fixes: a94d4e1 ("add APK signing logic")
Signed-off-by: Petr Štetiar <ynezz@true.cz>

phase2/master.cfg

@@ -591,7 +591,8 @@ for arch in arches:
 			name = "signpack",
 			description = "Packing files to sign",
 			workdir = "build/sdk",
-			command = "find bin/packages/%s/ -mindepth 2 -maxdepth 2 -type f " %(arch[0])
+			command = "find bin/packages/%s/ -mindepth 1 -maxdepth 2 -type f " %(arch[0])
+			+ "-name sha256sums -print0 -or "
 			+ "-name Packages -print0 -or "
 			+ "-name packages.adb -print0 | "
 			+ "xargs -0 tar -czf sign.tar.gz"