[PATCH] libxl: fix libacpi dependency

[Jan Beulich <jbeulich@suse.com>]

$(DSDT_FILES-y) depends on the recursive make to have run in libacpi/
such that the file(s) itself/themselves were generated before
compilation gets attempted. The same, however, is also necessary for
generated headers, before source files including them would get
attempted to be compiled.

The dependency specified in libacpi's Makefile, otoh, is entirely
pointless nowadays - no compilation happens there anymore (except for
tools involved in building the generated files). Together with it, the
rule generating acpi.a also can go away.

Reported-by: Olaf Hering <olaf@aepfle.de>
Fixes: 14c0d328da2b ("libxl/acpi: Build ACPI tables for HVMlite guests")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
Arguably we might also use $(ACPI_OBJS) instead of specifying just the
one object file we know has respective #include directives.

--- a/tools/libacpi/Makefile
+++ b/tools/libacpi/Makefile
@@ -89,11 +89,6 @@ iasl:
 	@echo 
 	@exit 1
 
-build.o: ssdt_s3.h ssdt_s4.h ssdt_pm.h ssdt_tpm.h ssdt_laptop_slate.h
-
-acpi.a: $(OBJS)
-	$(AR) rc $@ $(OBJS)
-
 clean:
 	rm -f $(C_SRC) $(H_SRC) $(MK_DSDT) $(C_SRC:=.$(TMP_SUFFIX))
 	rm -f $(patsubst %.c,%.hex,$(C_SRC)) $(patsubst %.c,%.aml,$(C_SRC)) $(patsubst %.c,%.asl,$(C_SRC))
--- a/tools/libs/light/Makefile
+++ b/tools/libs/light/Makefile
@@ -32,7 +32,7 @@ ACPI_PATH  = $(XEN_ROOT)/tools/libacpi
 DSDT_FILES-$(CONFIG_X86) = dsdt_pvh.c
 ACPI_OBJS  = $(patsubst %.c,%.o,$(DSDT_FILES-y)) build.o static_tables.o
 ACPI_PIC_OBJS = $(patsubst %.o,%.opic,$(ACPI_OBJS))
-$(DSDT_FILES-y): acpi
+$(DSDT_FILES-y) build.o: acpi
 vpath build.c $(ACPI_PATH)/
 vpath static_tables.c $(ACPI_PATH)/