Make BuildLinkerConfig run in its own action

We should probably do this change for more parts of the filesystem
RuleBuilder. Moving the linker config action out of the filesystem
rulebuilder allows it to run in parallel with opther actions, and not
rerun every time the filesystem is rebuilt.

Bug: 384091387
Test: Presubmits
Change-Id: Ic7305c555260fb5d9900c6c709b6c81dc0708d2b