Adjust LLVM_ENABLE_ABI_BREAKING_CHECKS depending on NDEBUG

When assertions are disabled, the upstream build system disables
LLVM_ENABLE_ABI_BREAKING_CHECKS by default. Though the upstream build
system allows it to be force-enabled, it looks like that is not a
well-tested build-time configuration.

Therefore, always disable LLVM_ENABLE_ABI_BREAKING_CHECKS when
assertions are disabled, which will also save some more runtime cost
when people use WITHOUT_LLVM_ASSERTIONS.

PR: 280562
MFC after: 1 month