maint: cleanup up various uses of __attribute__

* src/cfg.mk (sc_prohibit-gl-attributes): Disallow the __attribute()
form without trailing underscores as that is not elided where required.
Also ensure we use gnulib macros rather than defining our own.
* src/system.h: Remove gnulib provided macros.
* src/chown-core.c: Likewise.
* src/chroot.c: Likewise.
* src/copy.c: Likewise.
* src/csplit.c: Likewise.
* src/dd.c: Likewise.
* src/expr.c: Likewise.
* src/extent-scan.c: Likewise.
* src/factor.c: Likewise.
* src/ls.c: Likewise.
* src/od.c: Likewise.
* src/paste.c: Likewise.
* src/ptx.c: Likewise.
* src/sort.c: Likewise.
* src/stat.c: Likewise.
* src/stty.c: Likewise.
* src/system.h: Likewise.
* src/tac.c: Likewise.
* src/test.c: Likewise.
* src/tsort.c: Likewise.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/tac.c b/src/tac.c
index c6a8cf695..5bf40a7e8 100644
--- a/src/tac.c
+++ b/src/tac.c
@@ -409,7 +409,7 @@ record_or_unlink_tempfile (char const *fn, FILE *fp)
 #else
 
 static void
-record_or_unlink_tempfile (char const *fn, FILE *fp ATTRIBUTE_UNUSED)
+record_or_unlink_tempfile (char const *fn, FILE *fp _GL_UNUSED)
 {
   unlink (fn);
 }