lib/syscall-stubs: Trigger regeneration on configheader changes

Before aosp/3527960, vm-x86_64-test_os built arm64 targets. Unfortunately, the
change does not trigger a full rebuild but causes the incremental build to fail.

This change introduces a dependency on generated files to configheader
to detect build configuration changes.

Bug: 399565091
Test: build.py vm-x86_64-test_os-userdebug
Change-Id: Ie3b9890e5c41796005015ed0175bd9d3a926178d