Add some more release-candidate steps

from PR #8758, removed item 9 which is not applicable to release branch
(cherry picked from commit 3dbe554c9b077fadbdd5457bc7f1467de113d6be)

Conflicts:
	Makefile
set MARCH on appveyor
add --retry 5 to curl flags in msys_build.sh
temporarily add this branch to appveyor.yml