x32: fix build regression

* linux/x32/arch_regs.h: New file.
* Makefile.am (EXTRA_DIST): Add it.
diff --git a/Makefile.am b/Makefile.am
index 86ea59b..bc8e357 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -335,6 +335,7 @@
 	linux/unix_diag.h		\
 	linux/userent.h			\
 	linux/userent0.h		\
+	linux/x32/arch_regs.h		\
 	linux/x32/errnoent1.h		\
 	linux/x32/ioctls_arch0.h	\
 	linux/x32/ioctls_arch1.h	\
diff --git a/linux/x32/arch_regs.h b/linux/x32/arch_regs.h
new file mode 100644
index 0000000..9064ca6
--- /dev/null
+++ b/linux/x32/arch_regs.h
@@ -0,0 +1 @@
+#include "x86_64/arch_regs.h"