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/intrin/flushfilebuffers.c

@@ -19,8 +19,10 @@
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/nt/files.h"
+#include "libc/nt/runtime.h"
 
 __msabi extern typeof(FlushFileBuffers) *const __imp_FlushFileBuffers;
+__msabi extern typeof(GetLastError) *const __imp_GetLastError;
 
 /**
  * Flushes buffers of specified file to disk.
@@ -36,6 +38,7 @@ __msabi extern typeof(FlushFileBuffers) *const __imp_FlushFileBuffers;
 textwindows bool32 FlushFileBuffers(int64_t hFile) {
   bool32 ok;
   ok = __imp_FlushFileBuffers(hFile);
-  NTTRACE("FlushFileBuffers(%ld) → %hhhd% m", hFile, ok);
+  NTTRACE("FlushFileBuffers(%ld) → {%hhhd, %d}", hFile, ok,
+          __imp_GetLastError());
   return ok;
 }