build: Fix boost and openssl detection scripts

Change-Id: I3a5ed9d589030454bde6e98ab2f1ad568e64adce
diff --git a/.waf-tools/openssl.py b/.waf-tools/openssl.py
index 4a5c01f..eb85462 100644
--- a/.waf-tools/openssl.py
+++ b/.waf-tools/openssl.py
@@ -44,7 +44,7 @@
                        define_name='HAVE_%s' % var,
                        uselib_store=var,
                        mandatory=mandatory,
-                       cflags="-I%s/include" % root,
+                       cxxflags="-I%s/include" % root,
                        linkflags="-L%s/lib" % root,
                        fragment=CODE)
     else: