Unregister engine on uninstall (#7594)

Signed-off-by: Alex Peterson <26804013+AMZN-alexpete@users.noreply.github.com>

cmake/Platform/Windows/Packaging/PostInstallSetup.wxs

@@ -36,6 +36,7 @@
                 <Directory Id="root.cmake.runtime" Name="runtime"/>
             </Directory>
             <Directory Id="root.python" Name="python"/>
+            <Directory Id="root.scripts" Name="scripts"/>
             <Directory Id="root.tools" Name="Tools">
                 <Directory Id="root.tools.redist" Name="Redistributables">
                     <Directory Id="root.tools.redist.cmake" Name="CMake"/>
@@ -61,5 +62,12 @@
             Execute="deferred"
             Impersonate="no"/>
 
+        <CustomAction Id="UnRegisterEngine"
+            ExeCommand="&quot;[SystemFolder]cmd.exe&quot; /C @&quot;[root.scripts]o3de.bat&quot; register --remove --this-engine"
+            Directory="INSTALL_ROOT"
+            Execute="immediate"
+            Return="ignore"
+            Impersonate="no"/>
+
     </Fragment>
 </Wix>

cmake/Platform/Windows/Packaging/Template.wxs.in

@@ -58,6 +58,10 @@
             <Custom Action="ConfigurePython" After="MoveCMake">
                 NOT Installed Or REINSTALL
             </Custom>
+            <!-- limit the unregister action to full uninstall -->
+            <Custom Action="UnRegisterEngine" After="InstallInitialize">
+                (NOT UPGRADINGPRODUCTCODE) AND (REMOVE="ALL")
+            </Custom>
         </InstallExecuteSequence>
 
         <UIRef Id="$(var.CPACK_WIX_UI_REF)" />