tools build: Add subdir support

Add support to make directory any time we build objects out of the tree
(O=/tmp/krava) and the output directory does not exist.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Cc: Alexis Berlemont <alexis.berlemont@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-h80ukls4o2kpr0e4c4bfln6u@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/build/Makefile.build

@@ -37,6 +37,11 @@ subdir-obj-y :=
 build-file := $(dir)/Build
 include $(build-file)
 
+# Create directory unless it exists
+quiet_cmd_mkdir = MKDIR    $(dir $@)
+      cmd_mkdir = mkdir -p $(dir $@)
+     rule_mkdir = $(if $(wildcard $(dir $@)),,@$(call echo-cmd,mkdir) $(cmd_mkdir))
+
 # Compile command
 quiet_cmd_cc_o_c = CC       $@
       cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
@@ -49,9 +54,11 @@ quiet_cmd_ld_multi = LD       $@
 
 # Build rules
 $(OUTPUT)%.o: %.c FORCE
+	$(call rule_mkdir)
 	$(call if_changed_dep,cc_o_c)
 
 $(OUTPUT)%.o: %.S FORCE
+	$(call rule_mkdir)
 	$(call if_changed_dep,cc_o_c)
 
 # Gather build data: