ARCH is not propagating to the install_openssl script properly

[reaperhulk]

sh install_openssl.sh ${ARCH} is not actually passing ARCH as we expect.

See the output in https://ci.cryptography.io/blue/organizations/jenkins/pyca%2Finfra/detail/PR-120/1/pipeline/50

This should be x86_64 but it's configuring for 686 because it's not seeing an arg provided to the script. It appears that the OpenSSL config script might be "smart" enough to ignore what we tell it and compile for 64-bit anyway (since the 64-bit manylinux1 wheels definitely work), but we should still fix this as it's basically only working due to luck.