Fix up linkage of Nasal tests inside CppUnit

Ensure correct test backend is used inside fgfs_test_suite

src/Main/CMakeLists.txt

@@ -59,6 +59,9 @@ flightgear_component(Main "${SOURCES}" "${HEADERS}" sentryIntegration.cxx)
 # the main() function
 set(MAIN_SOURCE
     bootstrap.cxx
+    # we only want this file when building FGFS, so it can't be
+    # part of fgfsObjects
+    ${CMAKE_SOURCE_DIR}/src/Scripting/NasalUnitTesting.cxx
 )
 
 # Set up the embedded resources.

src/Scripting/CMakeLists.txt

@@ -13,8 +13,10 @@ set(SOURCES
   NasalString.cxx
   NasalModelData.cxx
   NasalSGPath.cxx
-  NasalUnitTesting.cxx
   NasalFlightPlan.cxx
+  # we don't add this here becuase we need to exclude it the testSuite
+  # so it can't go nto fgfsObjects library
+  #   NasalUnitTesting.cxx
 )
 
 set(HEADERS

test_suite/FGTestApi/NasalUnitTesting_TestSuite.cxx

@@ -124,3 +124,8 @@ naRef initNasalUnitTestCppUnit(naRef nasalGlobals, naContext c)
     
   return naNil();
 }
+
+void shutdownNasalUnitTestInSim()
+{
+    // stub
+}