Bug#1106224: sbuild does not provision a working chroot when there is an http_proxy

[picca]

for the record here my solution

$unshare_mmdebstrap_extra_args = [
    "*" => [ '--aptopt=Acquire::http { Proxy "http://...";; }',
             '--aptopt=Acquire::https { Proxy "http://...";; }',
             '--customize-hook=echo "export http_proxy=http://...";  > 
"$1"/etc/environment',
             '--customize-hook=echo "export https_proxy=http://...";  > 
"$1"/etc/environment',
    ]
    ];