cmake: fail early if no module.h found

Commit 58d39d7 ('cmake: fix warning')
causes a little regression: if there is no tarantool/module.h header, we
should fail at the cmake stage. After the fix of the warning we'll fail
only at the building stage (when `make` is called). Here I return the
old behaviour (fail on the `cmake` stage) back.

See tarantool/tuple-keydef#20

Author: Totktonada

CMakeLists.txt

@@ -8,7 +8,7 @@ endif()
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}" ${CMAKE_MODULE_PATH})
 
 # Find Tarantool and Lua dependencies
-set(TARANTOOL_FIND_REQUIRED ON)
+set(Tarantool_FIND_REQUIRED ON)
 find_package(Tarantool)
 include_directories(${TARANTOOL_INCLUDE_DIRS})