Fix cross builds

[jw3]

Exclude s390x and ppc64le arches to avoid a known issue building the ring crate on these arches.

• https://bugzilla.redhat.com/show_bug.cgi?id=1869980

This also changes the wheel install to properly reference the target architecture when in a cross build.

Closes #751 Closes #752

[jw3]

Once the fix is verified the following can be added to our bz issue.

---

This package will be excluding the s390x and ppc64le arches to avoid a known issue building the ring crate.

Per the packaging guidelines, a reference to bz 1869980 has been added next to the ExcludeArch line.

• https://bugzilla.redhat.com/show_bug.cgi?id=1869980
• https://docs.fedoraproject.org/en-US/packaging-guidelines/#_architecture_build_failures