cmake for carl: handle situation where carl version information is missing

Older carl versions don't provide detailed version information, so we
provide an informative error message instead of cmake syntax errors during
the comparison.

resources/3rdparty/CMakeLists.txt

@@ -215,6 +215,10 @@ if(USE_CARL)
         else()
             message(SEND_ERROR "File ${carlLOCATION} does not exist, did you build carl?")
         endif()
+        if("${carl_MINORYEARVERSION}" STREQUAL "" OR "${carl_MINORMONTHVERSION}" STREQUAL "" OR "${carl_MAINTENANCEVERSION}" STREQUAL "")
+            # don't have detailed version information, probably an old version of carl
+            message(FATAL_ERROR "Carl at ${carlLOCATION} outdated, require ${CARL_MINYEAR}.${CARL_MINMONTH}.${CARL_MINPATCH}, have ${carl_VERSION}")
+        endif()
         if(${carl_MINORYEARVERSION} LESS ${CARL_MINYEAR})
             message(SEND_ERROR "Carl outdated, require ${CARL_MINYEAR}.${CARL_MINMONTH}.${CARL_MINPATCH}, have ${carl_VERSION}")
         elseif(${carl_MINORYEARVERSION} EQUAL ${CARL_MINYEAR})