cmake: Workaround for the FATAL_ERROR that occurred whenever building shipped carl was aborted (bypassing github issue #62).

resources/3rdparty/CMakeLists.txt

@@ -260,15 +260,27 @@ if (NOT STORM_FORCE_SHIPPED_CARL)
 		find_package(carl QUIET)
     endif()
 endif()
+
+set(STORM_SHIPPED_CARL OFF)
 if(carl_FOUND AND NOT STORM_FORCE_SHIPPED_CARL)
     get_target_property(carlLOCATION lib_carl LOCATION)
     if("${carlLOCATION}" STREQUAL "carlLOCATION-NOTFOUND")
+        if(EXISTS ${STORM_3RDPARTY_BINARY_DIR}/carl)
+            message(WARNING "Storm - Library for carl location is not found but the directory ${STORM_3RDPARTY_BINARY_DIR}/carl exists. Will (re-)try to build a shipped version of carl.")
+            set(STORM_SHIPPED_CARL ON)
+        else()
             message(FATAL_ERROR "Library location for carl is not found, did you build carl?")
+        endif()
     elseif(EXISTS ${carlLOCATION})
         #empty on purpose
+    else()
+        if(EXISTS ${STORM_3RDPARTY_BINARY_DIR}/carl)
+            message(WARNING "Storm - File ${carlLOCATION} does not exist but the directory ${STORM_3RDPARTY_BINARY_DIR}/carl exists. Will (re-)try to build a shipped version of carl.")
+            set(STORM_SHIPPED_CARL ON)
         else()
             message(FATAL_ERROR "File ${carlLOCATION} does not exist, did you build carl?")
         endif()
+    endif()
     if("${carl_VERSION_MAJOR}" STREQUAL "${CARL_C14VERSION}")
         message(STATUS "Storm - Found carl using master14 branch.")
         # empty on purpose. Maybe put a warning here?
@@ -276,7 +288,6 @@ if(carl_FOUND AND NOT STORM_FORCE_SHIPPED_CARL)
         message(FATAL_ERROR "Carl outdated, require ${CARL_MINVERSION}, have ${carl_VERSION}")
     endif()
 
-    set(STORM_SHIPPED_CARL OFF)
     set(STORM_HAVE_CARL ON)
     message(STATUS "Storm - Use system version of carl.")
     message(STATUS "Storm - Linking with preinstalled carl ${carl_VERSION} (include: ${carl_INCLUDE_DIR}, library ${carl_LIBRARIES}, CARL_USE_CLN_NUMBERS: ${CARL_USE_CLN_NUMBERS}, CARL_USE_GINAC: ${CARL_USE_GINAC}).")
@@ -284,6 +295,9 @@ if(carl_FOUND AND NOT STORM_FORCE_SHIPPED_CARL)
     set(STORM_HAVE_GINAC ${CARL_USE_GINAC})
 else()
     set(STORM_SHIPPED_CARL ON)
+endif()
+
+if (STORM_SHIPPED_CARL)
 	# The first external project will be built at *configure stage*
 	message(STATUS "Carl - Start of config process")
 	file(MAKE_DIRECTORY ${STORM_3RDPARTY_BINARY_DIR}/carl_download)