Get threads working well on MacOS Arm64

- Now using 10x better GCD semaphores
- We now generate Linux-like thread ids
- We now use fast system clock / sleep libraries
- The APE M1 loader now generates Linux-like stacks

third_party/nsync/mu_semaphore_sem.c

@@ -29,6 +29,10 @@
 #include "third_party/nsync/time.h"
 // clang-format off
 
+/**
+ * @fileoverview Semaphores w/ POSIX Semaphores API.
+ */
+
 #define ASSERT(x) _npassert(x)
 
 struct sem {