component/tcl: Switch to shared

Use @@LOCATION@@ template to provide proper prefix path.

component/tcl/buildout.cfg

@@ -5,8 +5,8 @@ parts = tcl
 recipe = slapos.recipe.cmmi
 url = http://prdownloads.sourceforge.net/tcl/tcl8.5.15-src.tar.gz
 md5sum = f3df162f92c69b254079c4d0af7a690f
-location = ${buildout:parts-directory}/${:_buildout_section_name_}
+shared = true
 configure-command = ./unix/configure
 configure-options =
-  --prefix=${:location}
+  --prefix=@@LOCATION@@
   --with-encoding=utf-8