Fail target if running configure or cmake fails

* src/appimage/appimage.mk.in (SETVARS): Set pipefail option.
($(stampdir)/stamp-$(1)-02-configure): Make touching the stamp file a
separate statement.

We need to set the pipefail option because otherwise the "| tee [...]"
after the configure/cmake calls hides a failure of configure/cmake.

• GnuPG-bug-id: T5592