Unbreak 'make dist' following recent commits.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@11605 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/Makefile.vex.am b/Makefile.vex.am
index 26b0278..3fa6190 100644
--- a/Makefile.vex.am
+++ b/Makefile.vex.am
@@ -25,6 +25,7 @@
 	pub/libvex_guest_ppc64.h \
 	pub/libvex_guest_arm.h \
 	pub/libvex_guest_s390x.h \
+	pub/libvex_s390x_common.h \
 	pub/libvex_ir.h \
 	pub/libvex_trc_values.h