test: Ignore codegen/x86_mmx.rs on s390x
test: Ignore codegen/x86_mmx.rs on s390x

graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust