/usr/lib/gcc-cross/s390x-linux-gnu/5/include/ is in libgcc-5-dev-s390x-cross 5.5.0-12ubuntu1cross1.
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/usr/lib/gcc-cross/s390x-linux-gnu/5/include-fixed/README
/usr/lib/gcc-cross/s390x-linux-gnu/5/include-fixed/limits.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include-fixed/syslimits.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/backtrace-supported.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/backtrace.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/float.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/htmintrin.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/htmxlintrin.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/iso646.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/omp.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/openacc.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/s390intrin.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stdalign.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stdarg.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stdatomic.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stdbool.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stddef.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stdfix.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stdint-gcc.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stdint.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/stdnoreturn.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/unwind.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/varargs.h
/usr/lib/gcc-cross/s390x-linux-gnu/5/include/vecintrin.h