builtins - low-level target-specific hooks required by code generation and other
runtime components
sanitizer runtimes - AddressSanitizer, ThreadSanitizer, UndefinedBehaviorSanitizer,
MemorySanitizer, LeakSanitizer, DataFlowSanitizer
profile - library which is used to collect coverage information
BlocksRuntime - target-independent implementation of Apple "Blocks" runtime
interfaces