linux-perf: Fix build-time check for unversioned files

The current check has never worked because the find -path predicate
matches against the whole path, including the given root.  In this
case that is $DESTDIR which always includes the version string.
Change to use cd before find.

Also, check all non-directories rather than all entries with "perf" in
the name.

debian/changelog

@@ -1,7 +1,11 @@
 linux (4.19.9-2) UNRELEASED; urgency=medium
 
+  [ Uwe Kleine-König ]
   * [arm] Fix probing of 3rd gpio device on Armada 370.
 
+  [ Ben Hutchings ]
+  * linux-perf: Fix build-time check for unversioned files
+
  -- Uwe Kleine-König <ukleinek@debian.org>  Mon, 17 Dec 2018 11:27:32 +0100
 
 linux (4.19.9-1) unstable; urgency=medium

debian/rules.d/tools/perf/Makefile

@@ -76,6 +76,6 @@ endif
 		$(DESTDIR)/usr/share/bash-completion/completions
 	rmdir --ignore-fail-on-non-empty $(DESTDIR)/etc
 # Check for unversioned files that are likely to result in file conflicts
-	! find $(DESTDIR) -name '*perf*' \! -path '*[_-]$(VERSION)*' | grep .
+	cd $(DESTDIR) && ! find \! -type d \! -path '*[_-]$(VERSION)*' | grep .
 
 endif # !nopython