sendmail: fix building as non-root user

sendmail: fix building as non-root user

Buildbot builds started failing with this:

[...]
install -c -o buildbot -g buildbot -m 644 ../../include/libmilter/mfapi.h /builder/shared-workdir/build/sdk/build_dir/target-x86_64_musl/sendmail-8.16.1/ipkg-install/usr/include/libmilter/mfapi.h
install: invalid user 'buildbot'

Extend 010-enable-nonroot-install.patch to remove "-o U -g G" from more
install targets.

Signed-off-by: W. Michael Petullo <redacted>