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/ls.c b/src/ls.c
index f1ed43bd2..d9876f842 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -2734,7 +2734,7 @@ has_capability (char const *name)
 }
 #else
 static bool
-has_capability (char const *name ATTRIBUTE_UNUSED)
+has_capability (char const *name _GL_UNUSED)
 {
   errno = ENOTSUP;
   return false;