[cmake,bugfix] Fixes requiredness of module

Previously, dependencies were not correctly searched for as
required packages. This patch fixes this.

bin/duneproject

@@ -481,7 +481,7 @@ if(NOT (dune-common_DIR OR dune-common_ROOT OR
 endif()
 
 #find dune-common and set the module path
-find_package(dune-common)
+find_package(dune-common REQUIRED)
 list(APPEND CMAKE_MODULE_PATH "\${PROJECT_SOURCE_DIR}/cmake/modules"
   \${dune-common_MODULE_PATH})
 

cmake/modules/DuneMacros.cmake

@@ -214,7 +214,7 @@ macro(dune_process_dependency_leafs modules versions is_required next_level_deps
     math(EXPR length "${mlength}-1")
     foreach(i RANGE 0 ${length})
       list(GET mmodules ${i} _mod)
-      find_dune_package(${_mod} ${REQUIRED})
+      find_dune_package(${_mod} ${is_required})
       set(${_mod}_SEARCHED ON)
       if(NOT "${is_required}" STREQUAL "")
         set(${_mod}_REQUIRED ON)