Exclude architectures
Outside of x86_64, ESS also uses the following platforms (more/different ones may appear in the future):
- IOxOS IFC14xx- (NXP QorIQ PowerPC 64-bit)
- Concurrent AMG6x/AM900 (Intel XEON/ Core-i7 64-bit)
If building with cross-compilers enabled (e3 feature - if you have cross-compilers available and sourced upon initial setup, these will be used for all consecutive builds), autotools will configure for x86_64 and then fail for cross-builds