cmake: improve InfiniTime_DIR default

With the old default of just "InfiniTime" you have to have the working
directory in the `InfiniSim` directory. The new default makes the
default independent of the current working directory.

Author: NeroBurner

CMakeLists.txt

@@ -1,7 +1,7 @@
 message(STATUS "Using CMake version ${CMAKE_VERSION}")
 cmake_minimum_required(VERSION 3.10...${CMAKE_VERSION})
 
-SET(InfiniTime_DIR "InfiniTime" CACHE PATH "Path to InfiniTime source path to use for simulator")
+SET(InfiniTime_DIR "${CMAKE_SOURCE_DIR}/InfiniTime" CACHE PATH "Path to InfiniTime source path to use for simulator")
 
 if(NOT EXISTS ${InfiniTime_DIR})
   message(FATAL_ERROR "Can't access folder '${InfiniTime_DIR}'. Try `git submodule update --init --recursive` to initialize the git submodule of InfiniTime")