Relax dpkg version regex

For non-release builds the version will include the number of commits since last release and the commit hash with dashes, e.g. 1.20.8-46-g0881.
For downstream distros it seems it may include their identification strings, e.g. 1.20.9ubuntu2.

Make the regex match everything after the version number to avoid incorrectly erroring on such versions.

Fixes #18

mmdebstrap

@@ -4498,7 +4498,7 @@ sub main() {
         # the --robot option was introduced in 1.20.0 but until 1.20.2 the
         # output contained a string after the version, separated by a
         # whitespace -- since then, it's only the version
-        if ($? == 0 and $content =~ /^([0-9.]+)( .*)?$/) {
+        if ($? == 0 and $content =~ /^([0-9.]+).*$/) {
             # dpkg is new enough for the --robot option
             $dpkgversion = version->new($1);
         }