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

libc/calls/fadvise-nt.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/createfileflags.internal.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/sig.internal.h"
 #include "libc/calls/state.internal.h"
@@ -41,17 +42,17 @@ static textwindows int sys_fadvise_nt_impl(int fd, uint64_t offset,
   h1 = g_fds.p[fd].handle;
   mode = g_fds.p[fd].mode;
   flags = g_fds.p[fd].flags;
-  flags &= ~(O_SEQUENTIAL | O_RANDOM);
+  flags &= ~(_O_SEQUENTIAL | _O_RANDOM);
 
   switch (advice) {
     case MADV_NORMAL:
       break;
     case MADV_RANDOM:
-      flags |= O_RANDOM;
+      flags |= _O_RANDOM;
       break;
     case MADV_WILLNEED:
     case MADV_SEQUENTIAL:
-      flags |= O_SEQUENTIAL;
+      flags |= _O_SEQUENTIAL;
       break;
     default:
       return einval();