CTest: Fix regression in build-and-test timeout compuatation

Refactoring in commit 66419bc046 (CTest: convert timeouts to
std::chrono::duration, 2017-11-20) accidentally changed the logic used
to compute the timeout for a test when it starts.  It incorrectly limits
the maximum possible timeout to 2 minutes rather than 2 minutes less
than the total allowed test time remaining.  Update the new logic to
restore the original behavior.

Avoid subtracting 2 minutes from our "infinite" timeout value to avoid
creating very large timeouts that are not "infinite" and may exceed
integer type ranges.

1 files changed, 4 insertions, 3 deletions

diff --git a/Source/cmCTest.cxx b/Source/cmCTest.cxx
index a4ca301..2cd60e5 100644
--- a/Source/cmCTest.cxx
+++ b/Source/cmCTest.cxx
@@ -1089,9 +1089,10 @@ int cmCTest::RunTest(std::vector<const char*> argv, std::string* output,
   bool modifyEnv = (environment && !environment->empty());
 
   // determine how much time we have
-  std::chrono::duration<double> timeout =
-    std::min<std::chrono::duration<double>>(this->GetRemainingTimeAllowed(),
-                                            std::chrono::minutes(2));
+  std::chrono::duration<double> timeout = this->GetRemainingTimeAllowed();
+  if (timeout != std::chrono::duration<double>::max()) {
+    timeout -= std::chrono::minutes(2);
+  }
   if (this->TimeOut > std::chrono::duration<double>::zero() &&
       this->TimeOut < timeout) {
     timeout = this->TimeOut;