Disallow in-source build to prevent issues

CMakeLists.txt

@@ -26,6 +26,18 @@ if(CXX_COMPILER_IS_DPCPP)
   message(STATUS "CXX compiler at ${CMAKE_CXX_COMPILER} detected as DPC++")
 endif()
 
+if ((CMAKE_CURRENT_BINARY_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR) OR
+  (CMAKE_CURRENT_BINARY_DIR STREQUAL ${CMAKE_CURRENT_SOURCE_DIR}/src) OR
+  (CMAKE_CURRENT_BINARY_DIR STREQUAL ${CMAKE_CURRENT_SOURCE_DIR}/include) OR
+  (CMAKE_CURRENT_BINARY_DIR STREQUAL ${CMAKE_CURRENT_SOURCE_DIR}/test) OR
+  (CMAKE_CURRENT_BINARY_DIR STREQUAL ${CMAKE_CURRENT_SOURCE_DIR}/examples) OR
+  (CMAKE_CURRENT_BINARY_DIR STREQUAL ${CMAKE_CURRENT_SOURCE_DIR}/vendor) OR
+  (CMAKE_CURRENT_BINARY_DIR STREQUAL ${CMAKE_CURRENT_SOURCE_DIR}/website))
+  message(FATAL_ERROR "Building in root or relevant directories will cause troubles.\nPLEASE use a build directory.")
+else()
+  message(STATUS "Build Dir is ${CMAKE_CURRENT_BINARY_DIR}")
+endif()
+
 # Find SYCL implementation.
 set(hipSYCL_MIN_VERSION "0.9.1")
 if(CELERITY_SYCL_IMPL STREQUAL "hipSYCL")