rust configure is misinvoking sed -i on Mac OS X

[pnkfelix]

These lines

        # Hack the tools Makefile to turn off the clang build
        sed -i 's/clang//g' tools/Makefile

are not correct for sed on OS X, where the extension for the backup files is required when using -i

% sed --help
sed: illegal option -- -
usage: sed script [-Ealn] [-i extension] [file ...]
       sed [-Ealn] [-i extension] [-e script] ... [-f script_file] ... [file ...]

I believe this is what causes the following output during configure:

sed: 1: "tools/Makefile": undefined label 'ools/Makefile'

[brson]

Clang is not in the tree now, so this configure step has no effect (unless ones workspace still has clang sitting around).

[pnkfelix]

Odd, I had thought I had seen it on relatively fresh workspaces. I guess I will double-check.

[pnkfelix]

Okay, I was confused by @brson's comment. I thought he was saying that this line should not be firing, but I think he is saying that it can be safely removed. (Thus I am not crazy, and one will indeed still see the message on fresh workspaces, or non-fresh ones, really anywhere you run configure on OS X.)

Anyway, I'll remove the line.