Incorrect Default Permissions in runc

runc is a CLI tool for spawning and running containers on Linux according to the OCI specification. A bug was found in runc prior to version 1.1.2 where `runc exec --cap` created processes with non-empty inheritable Linux process capabilities, creating an atypical Linux environment and enabling programs with inheritable file capabilities to elevate those capabilities to the permitted set during execve(2). This bug did not affect the container security sandbox as the inheritable set never contained more capabilities than were included in the container's bounding set. This bug has been fixed in runc 1.1.2. This fix changes `runc exec --cap` behavior such that the additional capabilities granted to the process being executed (as specified via `--cap` arguments) do not include inheritable capabilities. In addition, `runc spec` is changed to not set any inheritable capabilities in the created example OCI spec (`config.json`) file.