make lang/erlang-runtime23 package build reproducible

[sg2342_googlemail.com]

Summary

in order to make the package build reproducible, it is necessary to:

1. set configure arg '--disable-saved-compile-time' (supported since OTP-19.0)
2. replace generated timestamps in header files created by snmp mib compiler
3. replace generated timestamps in release script files created by reltool
4. set SOURCE_DATE_EPOCH to TIMESTAMP in PKG_ENV

Test Plan

run

poudriere bulk -C lang/erlang-runtime23

twice, compare the packages produced.

[sg2342_googlemail.com]

update path in diff, add PORTREVISION

[sg2342_googlemail.com]

after reading D24586 :

• the PKG_ENV change is not needed
• the post-build target must not extract the TIMESTAMP from ${DISTINFO_FILE}, it should use ${_TIMESTAMP} ?