Add mes and mescc-tools-extra

mescc-tools-extra contains two important tools:
- cp
- chmod

mes first builds itself from a mes 0.21 seed as used by guix, and then
builds a mes 0.22 and then mes 0.22 using that created mes 0.22.

It does /not/ use bootstrap.sh as we don't have a proper shell at this
point, it has been manually adapted for kaem.

sysa/mes-0.22/lib/linux/x86-mes-gcc/mini.c

@@ -0,0 +1,58 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2016,2017,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "mes/lib-mini.h"
+
+#define SYS_exit   "0x01"
+#define SYS_write  "0x04"
+
+// *INDENT-OFF*
+void
+_exit (int code)
+{
+  asm (
+       "mov    $"SYS_exit",%%eax\n\t"
+       "mov    %0,%%ebx\n\t"
+       "int    $0x80\n\t"
+       : // no outputs "=" (r)
+       : "rm" (code)
+       : "eax", "ebx"
+       );
+  // not reached
+  _exit (0);
+}
+
+ssize_t
+_write (int filedes, void const *buffer, size_t size)
+{
+  long r;
+  asm (
+       "mov    $"SYS_write",%%eax\n\t"
+       "mov    %1,%%ebx\n\t"
+       "mov    %2,%%ecx\n\t"
+       "mov    %3,%%edx\n\t"
+       "int    $0x80\n\t"
+       "mov    %%eax,%0\n\t"
+       : "=r" (r)
+       : "rm" (filedes), "rm" (buffer), "rm" (size)
+       : "eax", "ebx", "ecx", "edx"
+       );
+  return r;
+}