Sacado: Add option for turning off Gtest if desired.

This adds the option Sacado_ENABLE_GTest for turning off the Sacado GTest suite
(previously it was required if tests were turned on).  The included gtest does
not build on all platforms (for various reasons), so this allows one to turn
it off.

For issue #7778

packages/sacado/CMakeLists.txt

@@ -91,6 +91,11 @@ TRIBITS_ADD_OPTION_AND_DEFINE(${PACKAGE_NAME}_ENABLE_VIEW_SPEC
   "Enable Sacado specializations for Kokkos::View<...>"
   ON )
 
+TRIBITS_ADD_OPTION_AND_DEFINE(${PACKAGE_NAME}_ENABLE_GTest
+  HAVE_SACADO_GTEST
+  "Enable internal GTest library for unit testing"
+  ON )
+
 SET(Sacado_ENABLE_ADOLC_default OFF)
 IF(TPL_ENABLE_ADOLC)
   SET(Sacado_ENABLE_ADOLC_default ON)

packages/sacado/test/CMakeLists.txt

@@ -1,4 +1,6 @@
-ADD_SUBDIRECTORY(GTestSuite)
+IF (Sacado_ENABLE_GTest)
+  ADD_SUBDIRECTORY(GTestSuite)
+ENDIF()
 ADD_SUBDIRECTORY(UnitTests)
 ADD_SUBDIRECTORY(tradoptest)
 ADD_SUBDIRECTORY(performance)