s390: Enable travis

We have to use "debian.jessie" instead of "ubuntu.xenial" because
qemu-s390x-static can only run z900 instructions and Ubuntu is
built with a more recent architecture level set.

We first enable only gcc because there are still some issues with clang.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

.travis.yml

@@ -13,6 +13,7 @@ env:
   - TR_ARCH=armv7hf
   - TR_ARCH=aarch64
   - TR_ARCH=ppc64le
+  - TR_ARCH=s390x
   - TR_ARCH=armv7hf     CLANG=1
   - TR_ARCH=aarch64     CLANG=1
   - TR_ARCH=ppc64le     CLANG=1

scripts/build/Dockerfile.s390x.hdr

+FROM s390x/debian:jessie
+
+ENV QEMU_CPU z900
+COPY scripts/build/qemu-user-static/usr/bin/qemu-s390x-static /usr/bin/qemu-s390x-static

scripts/build/Makefile

-QEMU_ARCHES := armv7hf aarch64 ppc64le # require qemu
+QEMU_ARCHES := armv7hf aarch64 ppc64le s390x # require qemu
 ARCHES := $(QEMU_ARCHES) x86_64
 TARGETS := $(ARCHES) alpine fedora-asan
 TARGETS_CLANG := $(addsuffix $(TARGETS),-clang)

scripts/build/binfmt_misc

@@ -8,3 +8,6 @@ test -f /proc/sys/fs/binfmt_misc/aarch64 ||
 
 test -f /proc/sys/fs/binfmt_misc/ppc64le ||
 	echo ':ppc64le:M::\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x15\x00:\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\x00:/usr/bin/qemu-ppc64le-static:' > /proc/sys/fs/binfmt_misc/register
+
+test -f /proc/sys/fs/binfmt_misc/s390x ||
+	echo ':s390x:M::\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x16:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/usr/bin/qemu-s390x-static:' > /proc/sys/fs/binfmt_misc/register