rules_r: compiler flags for reproducibility
rules_r: compiler flags for reproducibility

Summary:
These are better than the .so editing that is happening right now.

This still leaves some gaps when the absolute path of the files can make it as
a string in the library object, so it's not perfect.

Reviewers: ysaito

Reviewed By: ysaito

Differential Revision: https://phabricator.grailbio.com/D14394

fbshipit-source-id: f7d74d3

grailbio/rules_r,grailbio/rules_r,grailbio/rules_r,grailbio/rules_r,grailbio/rules_r