Make considerably more progress on AARCH64

- Utilities like pledge.com now build
- kprintf() will no longer balk at 48-bit addresses
- There's a new aarch64-dbg build mode that should work
- gc() and defer() are mostly pacified; avoid using them on aarch64
- THIRD_PART_STB now has Arm Neon intrinsics for fast image handling

test/libc/calls/diagnose_syscall_test.c

@@ -27,6 +27,8 @@
 #include "libc/sysv/consts/nr.h"
 #include "libc/testlib/testlib.h"
 
+#ifdef __x86_64__
+
 #define Z 0x5555555555555555
 
 #define FLAGS_cf 0
@@ -137,3 +139,5 @@ TEST(diagnose_syscall, testWriteFailed) {
     ASSERT_STREQ("rax rcx r11", _gc(DiffContexts(&x, &y)));
   }
 }
+
+#endif /* __x86_64__ */