replace egrep with grep -E

[moralground]

Building plan9port on modern Linux produces a log that's basically unreadable because of so many egrep warnings:

warning: egrep is obsolescent; using grep -E

It should be a pretty simple replace in the whole source tree.

[dancrossnyc]

But what about systems where egrep is not grep -E? A better fix would be to have an egrep wrapper she'll script that execs grep -E on Linux.

[moralground]

A better fix would be to have an egrep wrapper shell script that execs grep -E on Linux.

That's what egrep currently is on Linux, but with the obnoxious warning. I think the next version of coreutils will outright refuse to run it.

[dancrossnyc]

It is unfortunate that coreutils is breaking compatibility with the rest of the open source ecosystem in this way, as thwre are systems other than Linux (and even Linux-based systems that do not use the GNU utilities, such as Alpine). But the shell script wrapper I was referring to would probably be supplied by plan9ports.