awk: cmd. line:1: warning: regexp escape sequence `\=' is not a known regexp operator

[tonycoz]

I've been seeing the warning above in the logs for some smoke reports, for example http://perl.develop-help.com/dblog/5053641 .

POSIX documents \c where c isn't one of the defined escapes ('\', '\a', '\b', '\f' , '\n', '\r', '\t', '\v', '\ddd', '"', \/) that the behaviour is undefined.

This appears to be caused by https://github.com/Perl/metaconfig/blame/45e928bd4710417a6b63655f3b4f20d27deacd3a/U/modified/Cppsym.U#L272

Of course, this code has been in Configure since at least 1999, so it's not exactly urgent to fix this.