Define _GNU_SOURCE, required for O_CLOEXEC on uClibc

When building sysklogd on a uClibc system we must define _GNU_SOURCE to
get O_CLOEXEC.

Since _GNU_SOURCE is also required for asprintf() with GLIBC, as used by
the pidfile() replacement function, we drop it from there and rely on
AM_CPPFLAGS for all sources.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

lib/pidfile.c

@@ -31,7 +31,6 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
-#define _GNU_SOURCE		/* Needed with GLIBC to get asprintf() */
 #include <sys/stat.h>		/* utimensat() */
 #include <sys/time.h>		/* utimensat() on *BSD */
 #include <sys/types.h>

src/Makefile.am

@@ -36,7 +36,7 @@ endif
 AM_CFLAGS             = -W -Wall -Wextra
 AM_CFLAGS            += -Wno-unused-result -Wno-unused-parameter -fno-strict-aliasing
 AM_CPPFLAGS           = -DSYSCONFDIR=\"@sysconfdir@\" -DRUNSTATEDIR=\"@runstatedir@\"
-AM_CPPFLAGS          += -D_BSD_SOURCE -D_DEFAULT_SOURCE
+AM_CPPFLAGS          += -D_BSD_SOURCE -D_DEFAULT_SOURCE -D_GNU_SOURCE
 
 syslogd_SOURCES       = syslogd.c syslogd.h socket.c socket.h syslog.h
 syslogd_SOURCES      += timer.c timer.h queue.h compat.h