Warn the user if we can't find pkg-config

* configure.ac (WITH_IFAVAILABLE): Warn the user if we can't find
a usable pkg-config (bug#47159).

diff --git a/configure.ac b/configure.ac
index 1802c1baa1202dd4b88a147fc4f4195765f30037..2c62a9fe6f7fb9ccd2d6c741aa46f3979dddaf44 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -3897,6 +3897,11 @@ case $with_json,$HAVE_JSON in
      WITH_IFAVAILABLE="$WITH_IFAVAILABLE --with-json=ifavailable";;
 esac
 if test "X${MISSING}" != X; then
+  # If we have a missing library, and we don't have pkg-config installed,
+  # the missing pkg-config may be the reason.  Give the user a hint.
+  if test "X${PKG_CONFIG}" = X; then
+    AC_MSG_WARN([Unable to locate a usable pkg-config])
+  fi
   AC_MSG_ERROR([The following required libraries were not found:
     $MISSING
 Maybe some development libraries/packages are missing?