When compiling without diagnostic, I get a warning/error:

/Users/dda/wt/git/workgen-crash/test/csuite/wt3363_checkpoint_op_races/main.c:89:7: error: code will
never be executed [-Werror,-Wunreachable-code]
if (!testutil_is_flag_set("WT3363_CHECKPOINT_OP_RACES"))
1 error generated.

Here's my compiler version:

$ clang --version
Apple LLVM version 8.1.0 (clang-802.0.42)
Target: x86_64-apple-darwin16.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin