Make improvements

- More timspec_*() and timeval_*() APIs have been introduced.
- The copyfd() function is now simplified thanks to POSIX rules.
- More Cosmo-specific APIs have been moved behind the COSMO define.
- The setitimer() polyfill for Windows NT is now much higher quality.
- Fixed build error for MODE=aarch64 due to -mstringop-strategy=loop.
- This change introduces `make MODE=nox87 toolchain` which makes it
  possible to build programs using your cosmocc toolchain that don't
  have legacy fpu instructions. This is useful, for example, if you
  want to have a ~22kb tinier blink virtual machine.

tool/build/ar.c

@@ -30,7 +30,6 @@
 #include "libc/log/log.h"
 #include "libc/macros.internal.h"
 #include "libc/mem/arraylist2.internal.h"
-#include "libc/mem/copyfd.internal.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/sock/sock.h"
@@ -322,8 +321,8 @@ int main(int argc, char *argv[]) {
       goto fail;
     }
     outsize += (remain = sizes.p[i]);
-    if (_copyfd(fd, outfd, remain) == -1) {
-      reason = "copy_file_range failed";
+    if (copyfd(fd, outfd, remain) == -1) {
+      reason = "copy failed";
       goto fail;
     }
     close(fd);