cmCurl: Tolerate lack of CURLOPT_CAPATH support

Since curl 7.39 the CURLOPT_CAPATH setting may be rejected with a
CURLE_NOT_BUILT_IN error.  Simply tolerate this with silent failure
since we just will not use the CAPATH setting in this case.

Source/cmCurl.cxx

@@ -13,7 +13,7 @@
 #include "cmSystemTools.h"
 
 #define check_curl_result(result, errstr)                               \
-  if (result != CURLE_OK)                                               \
+  if (result != CURLE_OK && result != CURLE_NOT_BUILT_IN)               \
     {                                                                   \
     e += e.empty()? "" : "\n";                                          \
     e += errstr;                                                        \