Use gcc -x assembler-with-cpp instead of gcc -E --traditional

This patch makes it so we use "gcc -x assembler-with-cpp" to build our
.S files, instead of translating them to .s files and assembling
directly.  This allows us to use header files and simple symbolic
arithmetic more conveniently in .S files, and at the same time reduces
the number of temporary files created when building.

Signed-off-by: Peter Jones <pjones@redhat.com>

build32/Makefile

@@ -75,16 +75,14 @@ all: memtest.bin memtest.efi
 -include $(subst .o,.d,$(TST_OBJS))
 -include $(subst .o,.d,$(APP_OBJS))
 
-boot/%.o: boot/%.s
-	$(AS) $< -o $@
 
-boot/startup.s: ../boot/startup32.S ../boot/boot.h
+boot/startup.o: ../boot/startup32.S ../boot/boot.h
 	@mkdir -p boot
-	$(CC) -m32 -E -traditional -I../boot -o $@ $<
+	$(CC) -m32 -x assembler-with-cpp -c -I../boot -o $@ $<
 
-boot/%.s: ../boot/%.S ../boot/boot.h
+boot/%.o: ../boot/%.S ../boot/boot.h
 	@mkdir -p boot
-	$(CC) -m32 -E -traditional -I../boot -o $@ $<
+	$(CC) -m32 -x assembler-with-cpp -c -I../boot -o $@ $<
 
 boot/efisetup.o: ../boot/efisetup.c
 	@mkdir -p boot

build64/Makefile

@@ -74,16 +74,13 @@ all: memtest.bin memtest.efi
 -include $(subst .o,.d,$(TST_OBJS))
 -include $(subst .o,.d,$(APP_OBJS))
 
-boot/%.o: boot/%.s
-	$(AS) $< -o $@
-
-boot/startup.s: ../boot/startup64.S ../boot/boot.h
+boot/startup.o: ../boot/startup64.S ../boot/boot.h
 	@mkdir -p boot
-	$(CC) -E -traditional -I../boot -o $@ $<
+	$(CC) -x assembler-with-cpp -c -I../boot -o $@ $<
 
-boot/%.s: ../boot/%.S ../boot/boot.h
+boot/%.o: ../boot/%.S ../boot/boot.h
 	@mkdir -p boot
-	$(CC) -E -traditional -I../boot -o $@ $<
+	$(CC) -x assembler-with-cpp -c -I../boot -o $@ $<
 
 boot/efisetup.o: ../boot/efisetup.c
 	@mkdir -p boot