devel/re2: update to 20210202

Switch to CMake

Revert upstream commit 5bd6137 and slightly improve support

PR: ports/253255
Submitted by: daniel.engberg.lists@pyret.net
Approved by: maintainer timeout (sunpoet, 3w6d)
Tested: https://gitlab.com/swills/freebsd-ports/-/pipelines/259017091