gitlab-ci: Tell CDash when a test-ext job is done

These jobs are self-contained and so can be re-run on their own to
produce a whole new submission to CDash.  Tell CDash when each
submission is done so re-running a job replaces results rather than
accumulating them.

.gitlab/ci/ctest_test_external.cmake

@@ -28,6 +28,7 @@ ctest_submit(PARTS Update)
 ctest_submit(PARTS Configure)
 
 if (configure_result)
+  ctest_submit(PARTS Done)
   message(FATAL_ERROR
     "Failed to configure")
 endif ()
@@ -50,11 +51,13 @@ ctest_build(
 ctest_submit(PARTS Build)
 
 if (build_result)
+  ctest_submit(PARTS Done)
   message(FATAL_ERROR
     "Failed to build")
 endif ()
 
 if ("$ENV{CTEST_NO_WARNINGS_ALLOWED}" AND num_warnings GREATER 0)
+  ctest_submit(PARTS Done)
   message(FATAL_ERROR
     "Found ${num_warnings} warnings (treating as fatal).")
 endif ()
@@ -74,6 +77,9 @@ ctest_test(
 ctest_submit(PARTS Test)
 
 if (test_result)
+  ctest_submit(PARTS Done)
   message(FATAL_ERROR
     "Failed to test")
 endif ()
+
+ctest_submit(PARTS Done)