Enable ICF=safe for host binaries as well

We regressed binary size when we switch Darwin to use LLD, because
Darwin LD64 does ICF by default. Turn on ICF for host binaries to regain
the binary size savings (saves some space for Linux as well).

Test: presubmit
Bug: 236924555
Change-Id: I433062c3d263d69e431c1552faf1f18b13c5da42