build: Fix check for previously installed cython bindings
Due to the removal of pkg-config check for libxml2, $PKG_CONFIG was not
defined and a check for libplist's include dir via pkg-config failed.
By invoking PKG_PROG_PKG_CONFIG $PKG_CONFIG will be defined and the check
works again.
diff --git a/configure.ac b/configure.ac
index 61eb8ef..1daa614 100644
--- a/configure.ac
+++ b/configure.ac
@@ -113,6 +113,7 @@
CYTHON=false
fi
if [test "x$CYTHON" != "xfalse"]; then
+ PKG_PROG_PKG_CONFIG
AC_MSG_CHECKING([for libplist Cython bindings])
CYTHON_PLIST_INCLUDE_DIR=$($PKG_CONFIG --variable=includedir libplist)/plist/cython
if [test ! -d "$CYTHON_PLIST_INCLUDE_DIR"]; then
