perf tools: Fix version file for perf documentation with OUTPUT variable set

Fixes the following:

 + make OUTPUT=/.../.build/perf-user/ DESTDIR=/.../.install/perf-user/ man install-man
 make -C Documentation man
 make[1]: Entering directory `/.../.source/linux.perf/tools/perf/Documentation'
 make[2]: Entering directory `/.../.source/linux.perf/tools/perf'
 make[2]: *** No rule to make target `PERF-VERSION-FILE'.  Stop.

Signed-off-by: Robert Richter <robert.richter@amd.com>
Cc: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/1344361396-7237-2-git-send-email-robert.richter@amd.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/Makefile

@@ -195,10 +195,10 @@ install-pdf: pdf
 #install-html: html
 #	'$(SHELL_PATH_SQ)' ./install-webdoc.sh $(DESTDIR)$(htmldir)
 
-../PERF-VERSION-FILE: .FORCE-PERF-VERSION-FILE
-	$(QUIET_SUBDIR0)../ $(QUIET_SUBDIR1) PERF-VERSION-FILE
+$(OUTPUT)PERF-VERSION-FILE: .FORCE-PERF-VERSION-FILE
+	$(QUIET_SUBDIR0)../ $(QUIET_SUBDIR1) $(OUTPUT)PERF-VERSION-FILE
 
--include ../PERF-VERSION-FILE
+-include $(OUTPUT)PERF-VERSION-FILE
 
 #
 # Determine "include::" file references in asciidoc files.