Mark pattern labels as unremoveable

	Peephole optimization doesn't play well with find pattern at
	least. The only case when a pattern matching could have
	unreachable patterns is when we have lasgn/dasgn node, which
	shouldn't happen in real-life.

	Fixes https://bugs.ruby-lang.org/issues/17534
	---
	 compile.c                          |  2 +-
	 test/ruby/test_pattern_matching.rb | 10 ++++++++++
	 2 files changed, 11 insertions(+), 1 deletion(-)