build system: support for CUSTOM_TARGET_DEPS

doc/build_system.txt

@@ -362,6 +362,20 @@ in its 'LIBS' declaration and refers to the tools relative to
 '$(BUILD_BASE_DIR)'.
 
 
+Building additional custom targets accompanying library or program
+==================================================================
+
+There are cases when it is important to build additional targets
+besides standard files built for library or program. Of course there
+is no problem with writing specific make rules for commands that
+generate those target files but for them to be built a proper
+dependency must be specified. To achieve it those additional targets
+should be added to 'CUSTOM_TARGET_DEPS' variable like e.g. in
+iwl_firmware library from dde_linux repository:
+
+! CUSTOM_TARGET_DEPS += $(addprefix $(BIN_DIR)/,$(IMAGES))
+
+
 Automated integration and testing
 #################################
 

repos/base/mk/lib.mk

@@ -165,6 +165,11 @@ all: $(LIB_TAG)
 #
 $(LIB_TAG) $(OBJECTS): $(HOST_TOOLS)
 
+#
+# Trigger build of additional library specific targets
+#
+$(LIB_TAG): $(CUSTOM_TARGET_DEPS)
+
 $(LIB_TAG): $(LIB_A) $(LIB_SO) $(LIB_CHECKED) $(ABI_SO) $(INSTALL_SO) $(DEBUG_SO)
 	@touch $@
 

repos/base/mk/prg.mk

@@ -180,6 +180,11 @@ LINK_ITEMS_BRIEF := $(subst $(LIB_CACHE_DIR),$$libs,$(LINK_ITEMS))
 #
 $(LINK_ITEMS) $(TARGET): $(HOST_TOOLS)
 
+#
+# Trigger build of additional program specific targets
+#
+$(TARGET): $(CUSTOM_TARGET_DEPS)
+
 LD_CMD += -Wl,--whole-archive -Wl,--start-group
 LD_CMD += $(LINK_ITEMS_BRIEF)
 LD_CMD += $(EXT_OBJECTS)