CTest should write a JUnit XML test summary

This feature is to be used when testing Qt in Coin (our continuous
integration platform). The command line option --output-junit is
supported in CMake 3.21 or greater. However we have one particular
configuration that tests with CMake 3.16, so we exclude that one.

We have already configured the individual tests to print detailed
results in their own XML files, using QTest's functionality. But then,
when a qt test process crashes, it leaves behind a half-baked XML
file, or no file at all.

CTest on the contrary knows nothing about the internals of a Qt test,
and only cares about the process exit code. Even if a test crashes, it
catches that and reports it as a failure.

We enable this functionality here to use in addition to what QTest's
XML files provide, in order to collect more complete information on
test results.

Pick-to: 6.5
Task-number: QTQAINFRA-5146
Change-Id: I226203f93413689f5767a4d01ea1852b453ebf31
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Reviewed-by: Toni Saario <toni.saario@qt.io>
(cherry picked from commit 19aa21b595c7e523b6cc941580e55d8c6fc50a6d)

coin/instructions/cmake_run_ctest_enforce_exit_code.yaml

@@ -74,6 +74,15 @@ instructions:
       property: features
       contains_value: AbortTestingOnFirstFailure
 
+    # Enable CTest's JUnit XML summary only for recent versions
+  - type: AppendToEnvironmentVariable
+    variableName: CTEST_ARGS
+    variableValue: " --output-junit {{.Env.COIN_CTEST_RESULTSDIR}}{{.Env.CI_PATH_SEP}}test_summary.ctest_junit_xml"
+    enable_if:
+      condition: runtime
+      env_var: CMAKE_MIN_SUPPORTED_BIN_PATH
+      equals_value: null
+
   - type: EnvironmentVariable
     variableName: COIN_COMMAND_OUTPUT_TIMEOUT
     variableValue: "900"