kvm tools: Fix build of guest init with biarch powerpc compilers

On powerpc we build kvmtool as a 64bit binary. We do that by setting
-m64 in our CFLAGS. For most things we just call $(CC) and it passes
that info onto the linker.

However there is one place where we explicitly call the linker, in the
build of guest/init - and in that case we need to tell the linker to
build 64bit.

We have gotten away with this so far because we have been building with
a 64bit only toolchain. However if you build with a biarch toolchain,
which generally defaults to 32bit, we fail to link.

The fix is to defined LDFLAGS appropriately and pass it to LD.

Tested on powerpc and x86-64.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

Makefile

@@ -150,6 +150,7 @@ ifeq ($(ARCH), powerpc)
 	OBJS	+= powerpc/xics.o
 	ARCH_INCLUDE := powerpc/include
 	CFLAGS 	+= -m64
+	LDFLAGS += -m elf64ppc
 
 	ARCH_WANT_LIBFDT := y
 endif
@@ -348,7 +349,7 @@ $(PROGRAM_ALIAS): $(PROGRAM)
 $(GUEST_INIT): guest/init.c
 	$(E) "  LINK    " $@
 	$(Q) $(CC) -static guest/init.c -o $@
-	$(Q) $(LD) -r -b binary -o guest/guest_init.o $(GUEST_INIT)
+	$(Q) $(LD) $(LDFLAGS) -r -b binary -o guest/guest_init.o $(GUEST_INIT)
 
 $(DEPS):