[eglib] Fixed file being created without read/write permission on Win…

…dows.

This bug manifested itself as files being written to disk with 0 bytes.

Fixes the AOT compiler on Windows not working properly.

https://bugzilla.xamarin.com/show_bug.cgi?id=27900

eglib/src/gfile-win32.c

@@ -58,7 +58,7 @@ int mkstemp (char *tmp_template)
 	utf16_template = _wmktemp( utf16_template);
 	if (utf16_template && *utf16_template) {
 		/* FIXME: _O_TEMPORARY causes file to disappear on close causing a test to fail */
-		fd = _wopen( utf16_template, _O_BINARY | _O_CREAT /*| _O_TEMPORARY*/ | _O_EXCL, _S_IREAD | _S_IWRITE);
+		fd = _wopen( utf16_template, _O_BINARY | _O_CREAT /*| _O_TEMPORARY*/ | _O_RDWR | _O_EXCL, _S_IREAD | _S_IWRITE);
 	}
 
 	/* FIXME: this will crash if utf16_template == NULL */