Fix bochs bios build from a separate directory

Bochs keeps the BIOS-bochs-latest and BIOS-bochs-legacy binaries under revision
control.  Since the build changes these binaries, and guilt cannot handle
changed binaries, it makes it very difficult to work with a patch queue if
you're building from the same tree as the source is located.

Bochs has some support for building from a separate directory but it's currently
broken.  This patch fixes that and allows for a sane work flow when developing
BIOS changes for QEMU.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/bios/Makefile.in b/bios/Makefile.in
index 5c7bd4f..3d3d195 100644
--- a/bios/Makefile.in
+++ b/bios/Makefile.in
@@ -98,7 +98,7 @@ rombios32.bin: rombios32.out rombios.h
 	./biossums -pad $@
 
 rombios32.out: rombios32start.o rombios32.o rombios32.ld
-	ld -o $@ -T rombios32.ld rombios32start.o rombios32.o
+	ld -o $@ -T $(srcdir)/rombios32.ld rombios32start.o rombios32.o
 
 rombios32.o: rombios32.c acpi-dsdt.hex
 	$(GCC32) -O2 -Wall -c -o $@ $<
@@ -115,5 +115,4 @@ rombios32start.o: rombios32start.S
 BIOS-bochs-latest: rombios16.bin rombios32.bin
 	cat rombios32.bin rombios16.bin > $@
 
-biossums: biossums.c
-	$(GCC) -o biossums biossums.c
+biossums: biossums.o