ctest: Prevent infinite loop in ctest_run_script(NEW_PROCESS)

ctest passes an internal -SR argument to inform a subprocess which
script to run. Because all arguments are propagated to the subprocess,
nested subprocess receives multiple -SR arguments and re-runs
the parent script in addition to its own, leading to a loop.

Ignore redundant -SR arguments on input and also filter out parent's
-SR argument when constructing a child process.

Fixes: #8837

Source/CTest/cmCTestScriptHandler.cxx

@@ -97,7 +97,12 @@ int cmCTestScriptHandler::ExecuteScript(std::string const& total_script_arg)
     this->CTest->GetInitialCommandLineArguments();
   //*** need to make sure this does not have the current script ***
   for (size_t i = 1; i < initArgs.size(); ++i) {
-    argv.push_back(initArgs[i]);
+    // in a nested subprocess, skip the parent's `-SR <path>` arguments.
+    if (initArgs[i] == "-SR") {
+      i++; // <path>
+    } else {
+      argv.push_back(initArgs[i]);
+    }
   }
 
   // Now create process object

Source/cmCTest.cxx

@@ -1975,9 +1975,12 @@ int cmCTest::Run(std::vector<std::string> const& args)
   };
   auto const dashSR =
     [&runScripts, &SRArgumentSpecified](std::string const& script) -> bool {
-    SRArgumentSpecified = true;
-    runScripts.emplace_back(cmSystemTools::ToNormalizedPathOnDisk(script),
-                            true);
+    // -SR should be processed only once
+    if (!SRArgumentSpecified) {
+      SRArgumentSpecified = true;
+      runScripts.emplace_back(cmSystemTools::ToNormalizedPathOnDisk(script),
+                              true);
+    }
     return true;
   };
   auto const dash_S =