Add CET Shadow Stack Compatible flag (microsoft#5637)

Add CET Shadow Stack Compatible flag when building DXC to safeguard
against ROP/JOP attacks.

Fixes
[microsoft#5578](microsoft#5578)

Author: hekota

CMakeLists.txt

@@ -118,6 +118,11 @@ add_compile_options(/guard:cf)
 add_link_options(/guard:cf)
 endif(WIN32)
 
+# Enable CET Shadow Stack
+if(WIN32 AND NOT (CMAKE_GENERATOR_PLATFORM MATCHES "ARM.*"))
+add_link_options(/CETCOMPAT)
+endif(WIN32 AND NOT (CMAKE_GENERATOR_PLATFORM MATCHES "ARM.*"))
+
 # HLSL Change Ends
 
 # HLSL Change Starts - set flag for Appveyor CI