Since noux.mk is using a brute-force approach for setting
CFLAGS, CPPFLAGs etc. disable this check.

--- curl-7.29.0/configure.orig	2013-02-23 16:55:37.710076636 +0100
+++ curl-7.29.0/configure	2013-02-23 16:56:01.286193552 +0100
@@ -3671,8 +3671,8 @@
 
-  if test $xc_bad_var_libs = yes ||
-     test $xc_bad_var_cflags = yes ||
-     test $xc_bad_var_ldflags = yes ||
-     test $xc_bad_var_cppflags = yes; then
-     as_fn_error $? "Can not continue. Fix errors mentioned immediately above this line." "$LINENO" 5
-  fi
+#  if test $xc_bad_var_libs = yes ||
+#     test $xc_bad_var_cflags = yes ||
+#     test $xc_bad_var_ldflags = yes ||
+#     test $xc_bad_var_cppflags = yes; then
+#     as_fn_error $? "Can not continue. Fix errors mentioned immediately above this line." "$LINENO" 5
+#  fi