I have no idea why, but the installed "sed" wrapper never terminates
on RHEL. If I don't use the wrappen the the tools build fine, so this
just uses the already set autoconf variables to attempt to determine
if the system sed/awk are gsed/gawk and if they are then this avoids
using the wrappers.
There's a few oddities here:
* I have no idea why the sed wrapper fails, as it seems super safe.
* I haven't run into any awk problems, but I figured I'd treat it the
same as it isn't any harder.
* We shouldn't have to support 10 year old distributions.
Hopefully this doesn't break anyone's builds...
Select between curl(1), wget(1), and ftp(1) through autoconf.
Wherever possible, automatically follow HTTP location redirects and
enable passive FTP mode.
Explicitly instruct tar(1) to read from stdin since this is far from
universal behavior if unspecified: The default file is /dev/sa0 in
FreeBSD, /dev/rst0 in NetBSD and OpenBSD, etc.
Tests for program presence, such as those formerly embedded in the
top-level Makefile for gawk and gsed, are better suited for autoconf.
Note that it is not sufficient to merely export AWK and SED environment
variables, as packages may still directly invoke awk(1) and sed(1) with
non-standard features independent of the autotools framework.
Wrapper scripts therefore remain necessary, although these are now
generated by the configure script to avoid hard-coded paths.
Do not assume the existence of /bin/bash on all systems.
Palmer Dabbelt
Darius Rad
Albert Ou
Andrew Waterman