archiver.bbclass: enhance do_ar_recipe task signature

Previously, do_ar_recipe ran again unnecessarily when adding or
removing classes like buildhistory.bbclass, because that changes the
BBINCLUDED variable which do_ar_recipe uses to find .bbappend files.

This is both extra work and also sometimes triggered "basehash
changed" errors (seen under oe-selftest, which adds machine.inc and
bblayers.inc) because BBINCLUDED is special and does not cause
the basehash to be recalculated.

The file *content* already was not considered in the task signature,
instead relying indirectly on PF (which includes the revision assigned
by a PR server) to ensure that a new versioned source archive gets
created each time there is a rebuild.

Therefore it makes sense to use the same mechanism and also ignore the
file *list*, i.e. exclude BBINCLUDED from the task signature.

(From OE-Core rev: 9666f0e0b02efc14226c77497fd38f79fc372f98)

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/archiver.bbclass

@@ -330,6 +330,19 @@ python do_unpack_and_patch() {
         bb.utils.remove(src_orig, recurse=True)
 }
 
+# BBINCLUDED is special (excluded from basehash signature
+# calculation). Using it in a task signature can cause "basehash
+# changed" errors.
+#
+# Depending on BBINCLUDED also causes do_ar_recipe to run again
+# for unrelated changes, like adding or removing buildhistory.bbclass.
+#
+# For these reasons we ignore the dependency completely. The versioning
+# of the output file ensures that we create it each time the recipe
+# gets rebuilt, at least as long as a PR server is used. We also rely
+# on that mechanism to catch changes in the file content, because the
+# file content is not part of of the task signature either.
+do_ar_recipe[vardepsexclude] += "BBINCLUDED"
 python do_ar_recipe () {
     """
     archive the recipe, including .bb and .inc.