[DO NOT MERGE] Allow remote execution of link actions.

This CL adds a remoteexec package that allows adding a configurable RBE
prefix to the template.

Bug: b/166182389
Test: built aosp crosshatch userdebug with and without RBE_CXX_LINKS.
Change-Id: Ica920c3d7f79f2996210b9cbd448126451c1707c
Merged-In: Ica920c3d7f79f2996210b9cbd448126451c1707c