Shell: Make tests use PASS/FAIL instead of exit codes

There's no guarantee that the last executed command will have a zero
exit code, and so the shell exit code may or may not be zero, even if
all the tests pass.
Also changes the `test || echo fail && exit` to
`if not test { echo fail && exit }`, since that's nicer-looking.

Meta/Lagom/CMakeLists.txt

@@ -145,10 +145,13 @@ if (BUILD_LAGOM)
             get_filename_component(TEST_NAME ${TEST_PATH} NAME_WE)
             add_test(
                 NAME "Shell-${TEST_NAME}"
-                COMMAND shell_lagom "${TEST_PATH}"
-                WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+                COMMAND shell_lagom --skip-shellrc "${TEST_PATH}"
+                WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/../../Userland/Shell/Tests
             )
-            set_tests_properties("Shell-${TEST_NAME}" PROPERTIES TIMEOUT 10)
+            set_tests_properties("Shell-${TEST_NAME}" PROPERTIES
+                TIMEOUT 10
+                FAIL_REGULAR_EXPRESSION "FAIL"
+                PASS_REGULAR_EXPRESSION "PASS")
         endforeach()
     endif()
 endif()