mariabackup utility, binary path implementation for Mac.

implements in a native way get_exepath which gives reliably the full
path.

extra/mariabackup/xtrabackup.cc

@@ -61,6 +61,10 @@ Street, Fifth Floor, Boston, MA 02110-1335 USA
 #include <sys/resource.h>
 #endif
 
+#ifdef __APPLE__
+# include "libproc.h"
+#endif
+
 
 #include <btr0sea.h>
 #include <dict0priv.h>
@@ -6913,6 +6917,12 @@ static int get_exepath(char *buf, size_t size, const char *argv0)
   ssize_t ret = readlink("/proc/self/exe", buf, size-1);
   if(ret > 0)
     return 0;
+#elif defined(__APPLE__)
+  size_t ret = proc_pidpath(getpid(), buf, static_cast<uint32_t>(size));
+  if (ret > 0) {
+    buf[ret] = 0;
+    return 0;
+  }
 #endif
 
   return my_realpath(buf, argv0, 0);