build: Use flock to serialize ar steps as workaround

Use flock to serialize ar steps to avoid parallel build break
sometimes.

.gitignore

@@ -1,3 +1,4 @@
+.arlock
 .depend
 Make.dep
 *.o

Application.mk

@@ -130,9 +130,9 @@ $(CXXOBJS): %$(SUFFIX)$(OBJEXT): %$(CXXEXT)
 
 .built: $(OBJS)
 ifeq ($(WINTOOL),y)
-	$(call ARCHIVE, "${shell cygpath -w $(BIN)}", $(OBJS))
+	$(call ARLOCK, "${shell cygpath -w $(BIN)}", $(OBJS))
 else
-	$(call ARCHIVE, $(BIN), $(OBJS))
+	$(call ARLOCK, $(BIN), $(OBJS))
 endif
 	$(Q) touch $@
 

Make.defs

@@ -99,6 +99,10 @@ define REGISTER
 endef
 endif
 
+define ARLOCK
+	$(Q) flock .arlock $(call ARCHIVE, $1, $(2))
+endef
+
 # Tools
 
 ifeq ($(DIRLINK),)

Makefile

@@ -117,9 +117,9 @@ $(SYMTABOBJ): %$(OBJEXT): %.c
 
 $(BIN): $(SYMTABOBJ)
 ifeq ($(WINTOOL),y)
-	$(call ARCHIVE, "${shell cygpath -w $(BIN)}", $^)
+	$(call ARLOCK, "${shell cygpath -w $(BIN)}", $^)
 else
-	$(call ARCHIVE, $(BIN), $^)
+	$(call ARLOCK, $(BIN), $^)
 endif
 
 endif # !CONFIG_BUILD_LOADABLE
@@ -198,6 +198,7 @@ else
 		fi; \
 	)
 endif
+	$(call DELFILE, .arlock)
 	$(call DELFILE, .depend)
 	$(call DELFILE, $(SYMTABSRC))
 	$(call DELFILE, $(SYMTABOBJ))