[PATCH] uml: fix biarch gcc build on x86_64

I run an x86_64 kernel with i386 userspace (Ubuntu Dapper) and decided to try
out UML today.  I found that UML wasn't quite aware of biarch compilers (which
Ubuntu i386 ships).  A fix similar to what was done for x86_64 should probably
be committed (see
http://marc.theaimsgroup.com/?l=linux-kernel&m=113425940204010&w=2).  Without
the FLAGS changes, the build will fail at a number of places and without the
LINK change, the final link will fail.
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/Makefile-x86_64

@@ -6,9 +6,11 @@ START := 0x60000000
 
 #We #undef __x86_64__ for kernelspace, not for userspace where
 #it's needed for headers to work!
-CFLAGS += -U__$(SUBARCH)__ -fno-builtin
-USER_CFLAGS += -fno-builtin
+CFLAGS += -U__$(SUBARCH)__ -fno-builtin -m64
+USER_CFLAGS += -fno-builtin -m64
 CHECKFLAGS  += -m64
+AFLAGS += -m64
+LDFLAGS += -m elf_x86_64
 
 ELF_ARCH := i386:x86-64
 ELF_FORMAT := elf64-x86-64
@@ -16,3 +18,4 @@ ELF_FORMAT := elf64-x86-64
 # Not on all 64-bit distros /lib is a symlink to /lib64. PLD is an example.
 
 LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
+LINK-y += -m64

arch/um/kernel/vmlinux.lds.S

 #include <linux/config.h>
+/* in case the preprocessor is a 32bit one */
+#undef i386
 #ifdef CONFIG_LD_SCRIPT_STATIC
 #include "uml.lds.S"
 #else