src: scope switch-case declarations (-Wc++-compat)
The switch-statement form of the same diagnostic: a declaration with
an initializer sitting directly in a switch body is jumped over by the
following case labels
(-Werror,-Wjump-misses-init), which broke jloptions.o on the macOS
runners. Brace the affected case bodies, as master/release-1.12
already do: jloptions.c's -t/--threads and --gcthreads cases, and
ircode.c's TAG_RELOC_METHODROOT (not yet reached by the compiler, but
the same construct).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015p5nhLNtcnRfN1FdDdG2Vz