use PKG_PROG_PKG_CONFIG to set PKG_CONFIG correctly
diff --git a/configure.in b/configure.in
index 9de7217..2f2f156 100644
--- a/configure.in
+++ b/configure.in
@@ -110,6 +110,8 @@
 fi
 AC_MSG_RESULT($enable_generic_aesicm)
 
+PKG_PROG_PKG_CONFIG
+
 AC_MSG_CHECKING(whether to leverage OpenSSL crypto)
 AC_ARG_ENABLE(openssl,
   [AS_HELP_STRING([--enable-openssl],
@@ -188,7 +190,6 @@
 
 AC_CONFIG_HEADER(crypto/include/config.h:config_in.h)
 
-AC_CHECK_PROG(PKG_CONFIG, pkg-config, yes)
 if test "x$PKG_CONFIG" != "x"; then
     HAVE_PKG_CONFIG=1
     AC_CONFIG_FILES([libsrtp2.pc])