--- cpp/cmake_modules/DefineOptions.cmake
+++ cpp/cmake_modules/DefineOptions.cmake
@@ -76,7 +76,7 @@ macro(define_option_string name description default)
 endmacro()
 
 # Top level cmake dir
-if("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
+if(1)
   #----------------------------------------------------------------------
   set_option_category("Compile and link")
 
--- cpp/cmake_modules/ThirdpartyToolchain.cmake
+++ cpp/cmake_modules/ThirdpartyToolchain.cmake
@@ -1856,3 +1856,3 @@
-    find_package(RapidJSON ${ARROW_RAPIDJSON_REQUIRED_VERSION} HINTS "${CMAKE_ROOT}")
+    find_package(RapidJSON ${ARROW_RAPIDJSON_REQUIRED_VERSION} HINTS "${CMAKE_ROOT}" REQUIRED)
     if(RapidJSON_FOUND)
-      set(RAPIDJSON_INCLUDE_DIR ${RAPIDJSON_INCLUDE_DIRS})
+      set(RAPIDJSON_INCLUDE_DIR ${RapidJSON_INCLUDE_DIRS})