test(xCAT-test): cover the debootstrap architecture genimage passes

Drive the assignment genimage makes and check the name debootstrap receives for
each architecture, including the POWER LE spelling that debootstrap rejects.

xCAT-test/unit/ubuntu_genimage_debootstrap_arch.t

@@ -0,0 +1,44 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use File::Spec;
+use FindBin;
+use Test::More;
+
+# debootstrap takes the Debian architecture name, which differs from the name xCAT uses for
+# the node. Drive the assignment genimage makes and check the name it computes. The
+# invocation that consumes it is not exercised here.
+
+use lib "$FindBin::Bin/../lib";
+use lib "$FindBin::Bin/../../perl-xCAT";
+use xCAT::Utils;
+
+my $repo_root = File::Spec->rel2abs(File::Spec->catdir($FindBin::Bin, '..', '..'));
+my $genimage  = File::Spec->catfile(
+    $repo_root, 'xCAT-server', 'share', 'xcat', 'netboot', 'ubuntu', 'genimage');
+plan skip_all => "genimage not found at $genimage" unless -f $genimage;
+
+my $src = do { local $/; open my $fh, '<', $genimage or die $!; <$fh> };
+# Take every line that assigns $uarch, not just the first: the name has been built in
+# more than one statement before, and half of it would look like a different value.
+my ($assignment) = $src =~ /^(my \$uarch\b.*?)\n\s*\n/ms;
+ok(defined $assignment, 'found the debootstrap architecture assignment in genimage')
+  or do { done_testing(); exit };
+
+sub debootstrap_arch {
+    my ($arch) = @_;
+    my $uarch;
+    my $code = $assignment;
+    $code =~ s/^my\s+//;
+    no strict 'subs';    ## the script itself does not enable strict subs
+    eval "$code 1" or die $@;    ## no critic (BuiltinFunctions::ProhibitStringyEval)
+    return $uarch;
+}
+
+is(debootstrap_arch('x86_64'),  'amd64',   'x86_64 resolves to the Debian name amd64');
+is(debootstrap_arch('ppc64el'), 'ppc64el', 'the Debian spelling of POWER LE is kept');
+is(debootstrap_arch('ppc64le'), 'ppc64le', 'the POWER LE alias is passed through, as it is today');
+is(debootstrap_arch('s390x'),   's390x',   'an architecture Debian names the same is passed through');
+
+done_testing();