Make improvements

- You can now run `make -j8 toolchain` on Windows
- You can now run `make -j` on MacOS ARM64 and BSD OSes
- You can now use our Emacs dev environment on MacOS/Windows
- Fix bug where the x16 register was being corrupted by --ftrace
- The programs under build/bootstrap/ are updated as fat binaries
- The Makefile now explains how to download cosmocc-0.0.12 toolchain
- The build scripts under bin/ now support "cosmo" branded toolchains
- stat() now goes faster on Windows (shaves 100ms off `make` latency)
- Code cleanup and added review on the Windows signal checking code
- posix_spawnattr_setrlimit() now works around MacOS ARM64 bugs
- Landlock Make now favors posix_spawn() on non-Linux/OpenBSD
- posix_spawn() now has better --strace logging on Windows
- fstatat() can now avoid EACCES in more cases on Windows
- fchmod() can now change the readonly bit on Windows

third_party/make/main.c

@@ -971,7 +971,7 @@ reset_jobserver (void)
 int
 main (int argc, char **argv, char **envp)
 {
-  ShowCrashReports();
+  // ShowCrashReports();
 
   static char *stdin_nm = 0;
   int makefile_status = MAKE_SUCCESS;
@@ -982,7 +982,7 @@ main (int argc, char **argv, char **envp)
   int argv_slots;
 
   // [jart] workaround to prevent make -j fork bomb
-  default_load_average = __get_cpu_count();
+  default_load_average = __get_cpu_count() * 1.5;
   max_load_average = default_load_average;
 
   /* Useful for attaching debuggers, etc.  */
@@ -1042,10 +1042,6 @@ main (int argc, char **argv, char **envp)
 
 #undef  FATAL_SIG
 
-#ifndef NDEBUG
-  ShowCrashReports();
-#endif
-
   /* Do not ignore the child-death signal.  This must be done before
      any children could possibly be created; otherwise, the wait
      functions won't work on systems with the SVR4 ECHILD brain