Don't set autogen.sh KEY=VALUE arguments as environment variables

> Jan 18 15:18:25 <sberg> tml__, do you remember anything about
>  e3a07b8a ? looks odd to add configure
>  KEY=VALUE args to the environment
> Jan 18 15:18:27 <IZBot> core - Include environment variables already in
>  autogen.sh's environment -
>  http://cgit.freedesktop.org/libreoffice/core/commit/?id=e3a07b8a6cc03b6d5063e4da5a474d8c91a84b0a
> Jan 18 15:22:54 <tml__> sberg: not really any recollection, sorry
> Jan 18 15:23:09 <tml__> sberg: are you sure this isn't what makes it possible
>  to have CC=clang etc in autogen.input?
> Jan 18 15:24:07 <tml__> or maybe this is related to propagating stuff when
>  make re-runs autogen.sh?
> Jan 18 15:24:28 <sberg> tml__, configure already takes care itself of its
>  KEY=VALUE command line arguments
> Jan 18 15:24:36 <tml__> sad that I didn't write a better commit message
> Jan 18 15:24:55 <tml__> feel free to revert it, and see if anybody notices;)
> Jan 18 15:25:04 * cloph_away used it for CC/CXX and devtools repo
> Jan 18 15:26:11 <tml__> cloph_away: yes, but I think sberg says that should
>  work anyway, even without that commit

The only reading from ENV after that code in autogen.sh (both today and at the
time of e3a07b8a) is the

  if (defined $ENV{NOCONFIGURE}) {
      print "Skipping configure process.";

check, which would now no longer work if you pass NOCONFIGURE= as an argument
to autogen.sh (in autogen.input or on the command line) instead of as an
environment variable.

Change-Id: If50639978190d219b063ff39f81e29d2054c0443
Reviewed-on: https://gerrit.libreoffice.org/48133Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

autogen.sh

@@ -257,11 +257,6 @@ for my $arg (@cmdline_args) {
         push @args, $arg;
     }
 }
-for my $arg (@args) {
-    if ($arg =~ /^([A-Z]+)=(.*)/) {
-        $ENV{$1} = $2;
-    }
-}
 
 if (defined $ENV{NOCONFIGURE}) {
     print "Skipping configure process.";