ACPI: tools: Fix compilation when output directory is not present

Compiling the ACPI tools when output directory parameter is specified,
but the output directory is not present, triggers the following error:

make O=/data/test/tmp/ -C tools/power/acpi/

make: Entering directory '/data/src/kernel/linux/tools/power/acpi'
DESCEND tools/acpidbg
make[1]: Entering directory '/data/src/kernel/linux/tools/power/acpi/tools/acpidbg'
MKDIR include
CP include
CC tools/acpidbg/acpidbg.o
Assembler messages:
Fatal error: can't create /data/test/tmp/tools/power/acpi/tools/acpidbg/acpidbg.o: No such file or directory
make[1]: *** [../../Makefile.rules:24: /data/test/tmp/tools/power/acpi/tools/acpidbg/acpidbg.o] Error 1
make[1]: Leaving directory '/data/src/kernel/linux/tools/power/acpi/tools/acpidbg'
make: *** [Makefile:18: acpidbg] Error 2
make: Leaving directory '/data/src/kernel/linux/tools/power/acpi'

which occurs because the output directory has not been created yet.

Fix this issue by creating the output directory before compiling.

Reported-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Chen Yu <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
[ rjw: New subject, changelog edits ]
Signed-off-by: Rafael J. Wysocki <[e-mail]>

tools/power/acpi/Makefile.config

···
 ACPICA_INCLUDE := $(srctree)/../../../drivers/acpi/acpica
 CFLAGS += -D_LINUX -I$(KERNEL_INCLUDE) -I$(ACPICA_INCLUDE)
 CFLAGS += $(WARNINGS)
+MKDIR = mkdir
 
 ifeq ($(strip $(V)),false)
 	QUIET=@

tools/power/acpi/Makefile.rules

···
 
 $(objdir)%.o: %.c $(KERNEL_INCLUDE)
 	$(ECHO) "  CC      " $(subst $(OUTPUT),,$@)
+	$(QUIET) $(MKDIR) -p $(objdir) 2>/dev/null
 	$(QUIET) $(CC) -c $(CFLAGS) -o $@ $<
 
 all: $(OUTPUT)$(TOOL)