start build_monitor with 'belownormal' priority

[SVN r24094]

tools/regression/xsl_reports/runner/regression.py

@@ -369,7 +369,7 @@ def start_build_monitor( timeout ):
     if sys.platform == 'win32':
         build_monitor_path = tool_path( 'build_monitor.exe' )
         if os.path.exists( build_monitor_path ):
-            utils.system( [ 'start "" %s bjam.exe %d' % ( build_monitor_path, timeout*60 ) ] )
+            utils.system( [ 'start /belownormal %s bjam.exe %d' % ( build_monitor_path, timeout*60 ) ] )
         else:
             log( 'Warning: build monitor is not found at "%s"' % build_monitor_path )