windows requires -lwinhttp

ax_init_standard_project.m4

@@ -415,8 +415,12 @@ AC_DEFUN([AX_PKG_REQUIRE], [
   AC_SUBST(CPPFLAGS)
   AC_SUBST(CXXFLAGS)
   AC_SUBST(PKG_REQUIREMENTS)
-  if test -n "$3" -a "${$1_found}" != "no"; then
-    tmp_package=${$1_found}
+  if test -n "$3"; then
+    if test "${$1_found}" = "no"; then
+      tmp_package="yes"
+    else
+      tmp_package=${$1_found}
+    fi
     $1_found=no
     old_CPPFLAGS=${CPPFLAGS}
     CPPFLAGS=" ${$1_CFLAGS} ${CPPFLAGS}"
@@ -438,7 +442,7 @@ AC_DEFUN([AX_PKG_REQUIRE], [
         fi
       done
       if test "${$1_found}" = "no"; then
-        tmp_includedir=$(${ac_tool_prefix}pkg-config --variable=includedir $tmp_package)
+        tmp_includedir=$(${PKG_CONFIG} --variable=includedir $tmp_package)
         for x in ${tmp_includedir}; do
           AC_MSG_NOTICE([search for $3 in $x])
           for f in $(find ${x} -name "$3"); do