cmake: : link shec_utils against legacy-option-headers

cmake: : link shec_utils against legacy-option-headers

in c24a6ffe20, we tried to link all target dependent on legacy option
headers against legacy-option-headers, but we missed some of them.
in our CI, we spotted build failure like:
```
In file included from /home/jenkins-build/build/workspace/ceph-pull-requests/src/erasure-code/ErasureCode.cc:26:
In file included from /home/jenkins-build/build/workspace/ceph-pull-requests/src/osd/osd_types.h:41:
In file included from /home/jenkins-build/build/workspace/ceph-pull-requests/src/common/ceph_context.h:41:
In file included from /home/jenkins-build/build/workspace/ceph-pull-requests/src/common/config_proxy.h:6:
In file included from /home/jenkins-build/build/workspace/ceph-pull-requests/src/common/config.h:27:
In file included from /home/jenkins-build/build/workspace/ceph-pull-requests/src/common/config_values.h:59:
/home/jenkins-build/build/workspace/ceph-pull-requests/src/common/options/legacy_config_opts.h:1:10: fatal error: 'global_legacy_options.h' file not found
         ^~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
```
so in this change, we link the shec_utils to `legacy-option-headers`
as well to fulfill the build dependency.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>