Return when unreachable #287

Job	Run time
abi-dump-setup	1m 35s
Test lld / Lit Tests (ubuntu-22.04)	10m 25s
Build lldb / Lit Tests (ubuntu-22.04)	25m 24s
Test lld / Lit Tests (windows-2019)	1m 56s
Test llvm,clang,libclc / Lit Tests (ubuntu-22.04)	46m 32s
Build lldb / Lit Tests (windows-2019)	1m 58s
Test lld / Lit Tests (macOS-latest)	15m 35s
Test llvm,clang,libclc / Lit Tests (windows-2019)	2m 31s
Build lldb / Lit Tests (macOS-latest)	18m 37s
Test llvm,clang,libclc / Lit Tests (macOS-latest)	1h 9m 4s
abi-dump (build-baseline)	33m 42s
abi-dump (build-latest)	35m 59s
abi-compare	29s
	4h 23m 47s

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