shader: restore the handle build depth when a build throws

BuildHandleProgram incremented g_handle_depth and decremented it at the end, so
a NotImplementedException from BuildHandleNode left the thread-local depth above
zero. That thread never cleared g_handle_slots again, and stale IR::Inst* keys
from an earlier program could match instructions of a later one (a freed
instruction's address can be reused). Do the decrement and the outermost clear in
SCOPE_EXIT.

Follow-up to e23b0f2fab.

Assisted-by: Claude Sonnet 5.5 (implementation and commit message)

0 files changed, 0 insertions, 0 deletions