perf doc: Fix perfman.info build

Before this change 'make perfman.info' fails as cat-texi.perl is
missing. It also fails as the makeinfo output isn't written into the
appropriate file. Add cat-texi.perl from git. Add missing output file
flag for makeinfo.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https //lore.kernel.org/r/20210715013343.2286699-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/Makefile

@@ -331,7 +331,7 @@ $(OUTPUT)perfman.texi: $(MAN_XML) cat-texi.perl
 	mv $@+ $@
 
 $(OUTPUT)perfman.info: $(OUTPUT)perfman.texi
-	$(QUIET_MAKEINFO)$(MAKEINFO) --no-split --no-validate $*.texi
+	$(QUIET_MAKEINFO)$(MAKEINFO) --no-split --no-validate -o $@ $*.texi
 
 $(patsubst %.txt,%.texi,$(MAN_TXT)): %.texi : %.xml
 	$(QUIET_DB2TEXI)$(RM) $@+ $@ && \

tools/perf/Documentation/cat-texi.perl

@@ -0,0 +1,46 @@
+#!/usr/bin/perl -w
+
+use strict;
+use warnings;
+
+my @menu = ();
+my $output = $ARGV[0];
+
+open my $tmp, '>', "$output.tmp";
+
+while (<STDIN>) {
+	next if (/^\\input texinfo/../\@node Top/);
+	next if (/^\@bye/ || /^\.ft/);
+	if (s/^\@top (.*)/\@node $1,,,Top/) {
+		push @menu, $1;
+	}
+	s/\(\@pxref\{\[(URLS|REMOTES)\]}\)//;
+	s/\@anchor\{[^{}]*\}//g;
+	print $tmp $_;
+}
+close $tmp;
+
+print '\input texinfo
+@setfilename gitman.info
+@documentencoding UTF-8
+@dircategory Development
+@direntry
+* Git Man Pages: (gitman).  Manual pages for Git revision control system
+@end direntry
+@node Top,,, (dir)
+@top Git Manual Pages
+@documentlanguage en
+@menu
+';
+
+for (@menu) {
+	print "* ${_}::\n";
+}
+print "\@end menu\n";
+open $tmp, '<', "$output.tmp";
+while (<$tmp>) {
+	print;
+}
+close $tmp;
+print "\@bye\n";
+unlink "$output.tmp";