Mac OSX does not support date -R

ax_init_standard_project.m4

@@ -364,9 +364,9 @@ AC_DEFUN([AX_PKG_REQUIRE], [
       done
       if test ${$1_found} -eq 0; then
         for p in /usr/include ${$1_CFLAGS}; do
-          $1_file=$(find ${p#-I} -name $3)
+          $1_file=${p#-I}/$(find ${p#-I} -name $3)
           if test -e ${$1_file}; then
-            AC_MSG_WARN([Header file $3 found in ${p#-I}/${$1_file%/$3}])
+            AC_MSG_WARN([Header file $3 found in ${$1_file%/$3}])
             $1_CFLAGS="${$1_CFLAGS} -I${p#-I}/${$1_file%/$3}"
             $1_found=1
             break