BaseTools: Remove './SecMain' from 'run' target

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1561

When a target of 'run' is passed into build.py,
BaseTools unconditionally attempts to execute the
application called './SecMain' in the build output directory.

This behavior applies to the Nt32Pkg which is being
replaced with features in the EmulatorPkg.

Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>

BaseTools/Source/Python/build/build.py

@@ -1232,10 +1232,6 @@ class Build():
 
         # run
         if Target == 'run':
-            RunDir = os.path.normpath(os.path.join(AutoGenObject.BuildDir, GlobalData.gGlobalDefines['ARCH']))
-            Command = '.\SecMain'
-            os.chdir(RunDir)
-            LaunchCommand(Command, RunDir)
             return True
 
         # build modules