autoconf: Use ":" instead of "dnl" as a noop

Fixes #424.

diff --git a/configure.ac b/configure.ac
index 7f762fa31ba7e8d9e60dd9d2c5fa2dc2dc656afa..6021b760b517cfc72899ee8b49f1ecfc88f9f1a8 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -210,7 +210,7 @@ if test x"$use_ecmult_static_precomputation" != x"no"; then
   AC_RUN_IFELSE(
     [AC_LANG_PROGRAM([], [])],
     [working_native_cc=yes],
-    [working_native_cc=no],[dnl])
+    [working_native_cc=no],[:])
 
   CFLAGS_FOR_BUILD="$CFLAGS"