build: Add support for profiling perl modules

This allows to pass things like PERL_PROFILE=-d:NYTProf so that we can
generate profiling information.

debian/changelog

@@ -1,5 +1,9 @@
 dpkg (1.18.11) UNRELEASED; urgency=medium
 
+  [ Guillem Jover ]
+  * Build system:
+    - Add support for profiling perl modules.
+
   [ Updated manpages translations ]
   * German (Helge Kreutzmann).
 

run-script

@@ -16,4 +16,4 @@ export DPKG_DATADIR="$cwd"
 script="$1"
 shift 1
 
-exec $PERL "$cwd/$script" "$@"
+exec $PERL $PERL_PROFILE "$cwd/$script" "$@"