ARM semihosting: fix writing to stdout

SYS_FLEN would be called before a write on a descriptor to check its size.
Currently lseek would fail with -1 when given the stdout/stderr descriptor.
Changing to use fstat seems to be the standard way of handling this.

Signed-off-by: Spencer Oliver <ntfreak@users.sourceforge.net>

src/helper/system.h

@@ -50,6 +50,8 @@
 #ifdef _WIN32
 #include <winsock2.h>
 #include <ws2tcpip.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 #endif
 // --- platform specific headers ---