Runtime tests: fix creating tests in CMake build

During CMake, all runtime test files are copied into the CMake build
directory using add_custom_command which issues 'cmake -E copy ...'.
For some reason, the last file in the tests/runtime directory
(tests/runtime/watchpoint) is never copied which causes two issues:
- the watchpoint tests are never run in CI,
- even if the local setup already has tests/runtime/watchpoint in the
  build directory (it seems to have been working in the past), it is
  never updated.

I'm not sure if this is caused by our change or a CMake update, however,
our approach is IMHO not correct as it makes the runtime_tests target
depend on the runtime tests files from the source directory. Changing it
to depend on the (newly copied) files from the build directory
eliminates the above issue.

tests/CMakeLists.txt

@@ -123,14 +123,15 @@ add_custom_target(
 )
 add_test(NAME runtime_tests COMMAND ./runtime-tests.sh)
 
-file(GLOB_RECURSE runtime_test_files
+file(GLOB_RECURSE runtime_test_src_files
   RELATIVE ${CMAKE_CURRENT_SOURCE_DIR}
   CONFIGURE_DEPENDS
   runtime/*
 )
-list(REMOVE_ITEM runtime_test_files runtime/engine/cmake_vars.py)
+list(REMOVE_ITEM runtime_test_src_files runtime/engine/cmake_vars.py)
 
-foreach(runtime_test_file ${runtime_test_files})
+set(runtime_test_files)
+foreach(runtime_test_file ${runtime_test_src_files})
   add_custom_command(
     OUTPUT
       ${CMAKE_CURRENT_BINARY_DIR}/${runtime_test_file}
@@ -140,6 +141,10 @@ foreach(runtime_test_file ${runtime_test_files})
     DEPENDS
       ${CMAKE_CURRENT_SOURCE_DIR}/${runtime_test_file}
   )
+  list(APPEND
+    runtime_test_files
+    ${CMAKE_CURRENT_BINARY_DIR}/${runtime_test_file}
+  )
 endforeach()
 add_custom_target(runtime_test_files ALL DEPENDS ${runtime_test_files})
 add_dependencies(runtime_tests runtime_test_files)