cmake: create script only if SIMULATION is enabled

The simulation scripts are useless if the target is a real board and
not a QEMU simulation. Thus they will only be created if SIMULATION
is explicitly ON (-DSIMULATION=TRUE).
SIMULATION is disabled by default

Signed-off-by: ichdream <chensheng0802@outlook.com>
Change-Id: I8d2f27382e77f3f914d490ba7836364a99ca67d7

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a3b3bec..9b8b7a1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,12 +30,13 @@
 
 add_subdirectory(apps/sel4test-driver)
 
-include(simulation)
-if(KernelSel4ArchX86_64)
-    SetSimulationScriptProperty(MEM_SIZE "3G")
+if(SIMULATION)
+    include(simulation)
+    if(KernelSel4ArchX86_64)
+        SetSimulationScriptProperty(MEM_SIZE "3G")
+    endif()
+    if(KernelPlatformQEMUArmVirt)
+        SetSimulationScriptProperty(MEM_SIZE "2G")
+    endif()
+    GenerateSimulateScript()
 endif()
-if(KernelPlatformQEMUArmVirt)
-    SetSimulationScriptProperty(MEM_SIZE "2G")
-endif()
-
-GenerateSimulateScript()