Auto merge of #21242 - richo:no-perl, r=brson

There's only one build-critical path in which perl is used, and it was to do a text replacement trivially achievable with sed(1).

I ported the indenter script because it [appears to be used][indenter], but removed check links because it appears to be entirely out of date.

[indenter]: https://github.com/rust-lang/rust/blob/master/src/librustc/util/common.rs#L60-70

src/etc/check-links.pl

@@ -1,34 +0,0 @@
-#!/usr/bin/perl -w
-# Copyright 2014 The Rust Project Developers. See the COPYRIGHT
-# file at the top-level directory of this distribution and at
-# http://rust-lang.org/COPYRIGHT.
-#
-# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-# option. This file may not be copied, modified, or distributed
-# except according to those terms.
-
-my $file = $ARGV[0];
-
-my @lines = <>;
-
-my $anchors = {};
-
-my $i = 0;
-for $line (@lines) {
-    $i++;
-    if ($line =~ m/id="([^"]+)"/) {
-        $anchors->{$1} = $i;
-    }
-}
-
-$i = 0;
-for $line (@lines) {
-    $i++;
-    while ($line =~ m/href="#([^"]+)"/g) {
-        if (! exists($anchors->{$1})) {
-            print "$file:$i: $1 referenced\n";
-        }
-    }
-}

src/etc/indenter

@@ -1,16 +1,19 @@
-#!/usr/bin/perl
-use strict;
-use warnings;
+#!/usr/bin/env python
+import re
+import sys
 
-my $indent = 0;
-while (<>) {
-    if (/^rust: ~">>/) {
-        $indent += 1;
-    }
+indent = 0
+more_re = re.compile(r"^rust: ~\">>")
+less_re = re.compile(r"^rust: ~\"<<")
+while True:
+    line = sys.stdin.readline()
+    if not line:
+        break
 
-    printf "%03d  %s%s", $indent, ("  " x $indent), $_;
+    if more_re.match(line):
+        indent += 1
 
-    if (/^rust: ~"<</) {
-        $indent -= 1;
-    }
-}
+    print "%03d %s%s" % (indent, " " * indent, line.strip())
+
+    if less_re.match(line):
+        indent -= 1