At the moment the -m16 option only passes the "--32" parameter to the
assembler on glibc OSes, while on other OSes the assembler is called
without any specific flag. This is wrong and causes the assembler to
fail. Fix it by adding support for the -m16 option to x86-64.h.

2016-07-06  Roger Pau Monné  <roger.pau@citrix.com>

	* x86-64.h: append --32 to the assembler options when -m16 is used
	even on non-glibc OSes.

This should be backported to all stable branches up to 4.9 (when -m16 was
introduced).

--- UTC
--- gcc/config/i386/x86-64.h
+++ gcc/config/i386/x86-64.h
@@ -49,7 +49,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define WCHAR_TYPE_SIZE 32
 
 #undef ASM_SPEC
-#define ASM_SPEC "%{m32:--32} %{m64:--64} %{mx32:--x32}"
+#define ASM_SPEC "%{m16|m32:--32} %{m64:--64} %{mx32:--x32}"
 
 #undef ASM_OUTPUT_ALIGNED_BSS
 #define ASM_OUTPUT_ALIGNED_BSS(FILE, DECL, NAME, SIZE, ALIGN) \