glue depends.mk into the boilermake framework

we can't just `-include foo.la` from the source make files, as
they are evaluated by the boilermake framework.  Instead, we have
to jump through some additional hoops

scripts/boiler.mk

@@ -205,6 +205,15 @@ define ADD_TARGET_TO_ALL
 
 endef
 
+# ADD_TARGET_TO_ALL - Parameterized "function" that adds the target,
+#   and makes "all" depend on it.
+#
+#   USE WITH EVAL
+#
+define ADD_DEPENDS_MK
+    ALL_DEPENDS_MK += ${1}
+endef
+
 # ADD_TARGET_RULE.* - Parameterized "functions" that adds a new target to the
 #   Makefile.  There should be one ADD_TARGET_RULE definition for each
 #   type of target that is used in the build.
@@ -375,6 +384,7 @@ define INCLUDE_SUBMAKEFILE
     MAN :=
     FILES :=
     OUTPUT :=
+    DEPENDS_MK :=
 
     SUBMAKEFILES :=
 
@@ -509,6 +519,10 @@ define INCLUDE_SUBMAKEFILE
                          $$(call QUALIFY_PATH,$${DIR},$${MK})))))
     endif
 
+    ifneq "$${DEPENDS_MK}" ""
+        $$(eval $$(call ADD_DEPENDS_MK,$${DEPENDS_MK}))
+    endif
+
     # Reset the "current" target to it's previous value.
     TGT_STACK := $$(call POP,$${TGT_STACK})
     # If we're about to change targets, create the rules for the target
@@ -711,6 +725,14 @@ endif
 $(foreach D,$(patsubst %/,%,$(sort $(dir ${ALL_INSTALL}))),\
   $(eval $(call ADD_INSTALL_RULE.dir,${D})))
 
+#
+#  Now that all of the targets have been defined, include auto-build
+#  dependency files.
+#
+ifneq "$(ALL_DEPENDS_MK)" ""
+-include $(ALL_DEPENDS_MK)
+endif
+
 scan: ${ALL_PLISTS}
 
 .PHONY: clean.scan

src/tests/unit/all.mk

@@ -32,8 +32,7 @@ $(FILES.$(TEST)): export TZ = GMT
 #
 #  Look in each file for `proto foo`, and then make that file depend in `libfreeradius-foo.a`
 #
--include $(OUTPUT)/depends.mk
-
+DEPENDS_MK := $(OUTPUT)/depends.mk
 $(OUTPUT)/depends.mk: $(addprefix $(DIR)/,$(FILES)) | $(OUTPUT)
 	${Q}rm -f $@
 	${Q}touch $@