Issue #15968: Temporarily revert change to PCbuild/rt.bat

to prevent buildbot failures on test_idle.  This change
should go back in once #20035 is fixed.

PCbuild/rt.bat

@@ -30,13 +30,15 @@ set prefix=.\
 set suffix=
 set qmode=
 set dashO=
+set tcltk=tcltk
 
 :CheckOpts
 if "%1"=="-O" (set dashO=-O)     & shift & goto CheckOpts
 if "%1"=="-q" (set qmode=yes)    & shift & goto CheckOpts
 if "%1"=="-d" (set suffix=_d)    & shift & goto CheckOpts
-if "%1"=="-x64" (set prefix=amd64) & shift & goto CheckOpts
+if "%1"=="-x64" (set prefix=amd64) & (set tcltk=tcltk64) & shift & goto CheckOpts
 
+PATH %PATH%;%~dp0..\..\%tcltk%\bin
 set exe=%prefix%\python%suffix%
 set cmd=%exe% %dashO% -Wd -E -bb ../lib/test/regrtest.py %1 %2 %3 %4 %5 %6 %7 %8 %9
 if defined qmode goto Qmode