mountlist: suppress unused label warning on FreeBSD

Signed-off-by: Yury V. Zaytsev <yury@shurup.com>

configure.ac

@@ -66,6 +66,7 @@ ax_gcc_func_attribute_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
 _AC_LANG_PREFIX[]FLAGS=
 AX_GCC_FUNC_ATTRIBUTE([fallthrough])
 AX_GCC_FUNC_ATTRIBUTE([weak])
+AX_GCC_FUNC_ATTRIBUTE([unused])
 _AC_LANG_PREFIX[]FLAGS=$ax_gcc_func_attribute_save_flags
 unset ax_gcc_func_attribute_save_flags
 

lib/global.h

@@ -50,6 +50,12 @@
 #define MC_FALLTHROUGH
 #endif
 
+#ifdef HAVE_FUNC_ATTRIBUTE_UNUSED
+#define MC_UNUSED __attribute__((unused))
+#else
+#define MC_UNUSED
+#endif
+
 #ifdef USE_MAINTAINER_MODE
 #include "lib/logging.h"
 #endif

src/filemanager/mountlist.c

@@ -1215,7 +1215,7 @@ read_file_system_list (void)
 
     return g_slist_reverse (mount_list);
 
-  free_then_fail:
+  free_then_fail: MC_UNUSED;
     {
         int saved_errno = errno;