clang can't use pthread(s) flag

autogen.sh

@@ -5,7 +5,7 @@
 
 # Git hooks should come before autoreconf.
 if test -d .git; then
-  if ! test -d .git; then
+  if ! test -d .git/hooks; then
     mkdir .git/hooks
   fi
   ln -s -f ../../pre-commit.sh .git/hooks/pre-commit

m4/ax_pthread.m4

@@ -160,7 +160,11 @@ case ${host_os} in
         ;;
 
         darwin*)
+        if test "$CC" = "clang"; then 
+            ax_pthread_flags="$ax_pthread_flags"
+        else 
             ax_pthread_flags="-pthread $ax_pthread_flags"
+        fi
         ;;
 esac