[lmi] Working around a libarchive anomaly [Was: gcc-6.3 warnings for wx sha 41045df7]

[Greg Chicares]

On 2017-08-21 00:35, Greg Chicares wrote:
[...]
> I hope we can abandon gcc-4.9 and just use 6.3 for lmi: 6.3 seems to
> work perfectly well in a cygwin VM here, and we'll soon know whether
> that means it works in the office as well (as it certainly should).

BTW, to extract MinGW-w64's gcc-6.3 archive without upgrading cygwin
(thus, without upgrading 'bsdtar' or installing 'p7zip'), this is the
temporary workaround I tested:

cd /cache_for_lmi/downloads/
wget http://www.7-zip.org/a/7z1604.exe
chmod +x /cache_for_lmi/downloads/7z1604.exe
/cache_for_lmi/downloads/7z1604.exe

If cygwin's server were working reliably, I wouldn't mention '7zip'
because it includes non-free code, which 'p7zip' removes:
  https://cygwin.com/ml/cygwin-announce/2009-08/msg00003.html
Of course we won't use '7zip' for any purpose other than extracting
MinGW-w64 files.