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.

libc/calls/copy.c

@@ -0,0 +1,50 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/macros.internal.h"
+
+/**
+ * Copies data between file descriptors the old fashioned way.
+ *
+ * This function is intended for simple programs without signals. If
+ * signals are in play, then `SA_RESTART` needs to be used.
+ *
+ * @param in is input file descriptor
+ * @param out is input file descriptor
+ * @param n is number of bytes to exchange, or -1 for until eof
+ * @return bytes successfully exchanged, or -1 w/ errno
+ */
+ssize_t copyfd(int in, int out, size_t n) {
+  size_t i;
+  char buf[512];
+  ssize_t dr, dw;
+  for (i = 0; i < n; i += dr) {
+    dr = read(in, buf, MIN(n - i, sizeof(buf)));
+    if (dr == -1) return -1;
+    if (!dr) break;
+    dw = write(out, buf, dr);
+    if (dw == -1) return -1;
+    if (dw != dr) {
+      // POSIX requires atomic IO up to PIPE_BUF
+      // The minimum permissible PIPE_BUF is 512
+      __builtin_trap();
+    }
+  }
+  return i;
+}