internal/pkg: optionally register binfmt

This transparently supports curing foreign exec artifacts.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg_test.go

@@ -1289,6 +1289,11 @@ func TestErrors(t *testing.T) {
 		{"UnsupportedVariantError", pkg.UnsupportedVariantError(
 			"rosa",
 		), `unsupported variant "rosa"`},
+
+		{"UnsupportedArchError zero", pkg.UnsupportedArchError(""),
+			"invalid architecture name"},
+		{"UnsupportedArchError", pkg.UnsupportedArchError("riscv64"),
+			"unsupported architecture riscv64"},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {