Note that the select_arch macro changed in order to allow for its use within
a rule below arch_genrule. The command line settings were being manipulated in
a way that did not correctly propagate the select_arch select constraints.
PiperOrigin-RevId: 499651425
This requires several changes:
* Templates must preserve relevant tags.
* Pagetables templates are split into two targets, each preserving tags.
* The binary VDSO is similarly split into two targets, with some juggling.
* The top level tools/go_branch.sh now does a crossbuild of ARM64 as well,
and checks and merges the results of the two branches together.
Fixes#5178
PiperOrigin-RevId: 351304330