configure: avoid undefined check_for_ca_bundle

instead of using a "greater than 0" test, check for variable being
set, as it is always set to 1, and could be left unset if non of
OPENSSL MBEDTLS GNUTLS WOLFSSL is being configured for.

Closes #4213

diff --git a/configure.ac b/configure.ac
index 1ddc3d60100c2591154ecd3fe6a75142877db21f..020a0e08cee14854304bee76e517ec7f794484b1 100755 (executable)
--- a/configure.ac
+++ b/configure.ac
@@ -2633,7 +2633,7 @@ dnl **********************************************************************
 dnl Check for the CA bundle
 dnl **********************************************************************
 
-if test "$check_for_ca_bundle" -gt 0; then
+if test -n "$check_for_ca_bundle"; then
   CURL_CHECK_CA_BUNDLE
 fi