cmake: fix sccache job limits when dist is unavailable

cmake: fix sccache job limits when dist is unavailable

The "disabled" search only matches sccache's Disabled("disabled")
payload, not "dist-client feature not selected" or the NotConnected
states. Those reach the success branch, so the job counts become
SchedulerStatus-NOTFOUND, JOB_POOLS is never defined, and ninja
rejects the manifest. Key off the JSON lookup's error instead to
cover every non-dist state.

Signed-off-by: Sun Yuechi <sunyuechi@iscas.ac.cn>