Clang: Do not embed windows manifests if none is specified

Since commit b7385756 (Clang: embed windows manifests with GNU
interface, 2021-09-17, v3.22.0-rc1~107^2) we always pass the
`-Xlinker /MANIFEST:EMBED` flag to the linker.  This should be
done only if we also have `-Xlinker /MANIFESTINPUT:` flags.

Issue: #22611
Fixes: #23066
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