Fix aesmd service permission in linksgx.sh.

[yuguorui]

Currently sgx-aesm-service does not depend on any other sgx packages, which makes it difficult to guarantee the installation order of sgx-aesm-service. Specifically, sgx-aesm-service may be installed earlier than libsgx-ae-pce, but the user group sgx_prv was created by the latter.

This PR ensures that no matter what the order of package installation is, aesmd can have access to the sgx_provision device file.

[fqiu1]

It's legitimate to install sgx-aesm-service without creating sgx_prv group. For instance, some users might just want to load normal enclaves and don't want to use attestation.

[yuguorui]

It's legitimate to install sgx-aesm-service without creating sgx_prv group. For instance, some users might just want to load normal enclaves and don't want to use attestation.

Yes, you are right in non-DCAP platform.
But for DCAP scenarios, which runs upon CPUs support FLC, I do not find a situation where aesmd-service needs to be installed without attestation.

[veehaitch]

Please avoid absolute paths to executables. This assumes the host system adheres to the Filesystem Hierarchy Standard which is not always the case (a notable exception is Nix). Also see #730.

[yuguorui]

Please avoid absolute paths to executables. This assumes the host system adheres to the Filesystem Hierarchy Standard which is not always the case (a notable exception is Nix). Also see #730.

Sure, thanks for your comments.

I will push a new version later.