https://sourceforge.net/p/xmlrpc-c/code/3151
https://bugs.gentoo.org/870253
--- a/configure.in
+++ b/configure.in
@@ -696,7 +696,7 @@ dnl =======================================================================
 
 AC_MSG_CHECKING(for OpenSSL library)
 
-if pkg-config openssl; then
+if ${PKG_CONFIG} openssl; then
   HAVE_OPENSSL=yes
 else
   HAVE_OPENSSL=no
@@ -747,7 +747,7 @@ dnl =======================================================================
 
 AC_MSG_CHECKING(for Libxml2 library)
 
-if pkg-config libxml-2.0; then
+if ${PKG_CONFIG} libxml-2.0; then
   HAVE_LIBXML2=yes
 else
   HAVE_LIBXML2=no