Check for S_ISSOCK before use

	* src/filesystem/ops-common.h (make_file_type) [S_ISSOCK]: Only use
	S_ISSOCK when defined.

From-SVN: r254506

libstdc++-v3/ChangeLog

+2017-11-07  Jonathan Wakely  <jwakely@redhat.com>
+
+	* src/filesystem/ops-common.h (make_file_type) [S_ISSOCK]: Only use
+	S_ISSOCK when defined.
+
 2017-11-06  François Dumont  <fdumont@gcc.gnu.org>
 
 	* testsuite/libstdc++-prettyprinters/tr1.cc:  Compile with -O0.

libstdc++-v3/src/filesystem/ops-common.h

@@ -113,9 +113,11 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
       return file_type::fifo;
     else if (S_ISLNK(st.st_mode))
       return file_type::symlink;
+#ifdef S_ISSOCK // not present until POSIX:2001
     else if (S_ISSOCK(st.st_mode))
       return file_type::socket;
 #endif
+#endif
     return file_type::unknown;
   }