tools/nolibc: implement %m if errno is not defined

For improved compatibility, print %m as "unknown error" when nolibc is
compiled using NOLIBC_IGNORE_ERRNO.

Signed-off-by: Benjamin Berg <[e-mail]>
Signed-off-by: Thomas Weißschuh <[e-mail]>

tools/include/nolibc/stdio.h

···
 				if (!outstr)
 					outstr="(null)";
 			}
-#ifndef NOLIBC_IGNORE_ERRNO
 			else if (c == 'm') {
+#ifdef NOLIBC_IGNORE_ERRNO
+				outstr = "unknown error";
+#else
 				outstr = strerror(errno);
-			}
 #endif /* NOLIBC_IGNORE_ERRNO */
+			}
 			else if (c == '%') {
 				/* queue it verbatim */
 				continue;