Make:Improve directory generation portability.

Because of command differences in some build environments the "inline"
method of generating the build directory structure is not portable.
(e.g. in DOS environments the mkdir shell command fails if a directory
already exists, whereas in UNIX environments it succeeds.)

To improve portability we generate the directories needed using make,
but use the "order-only prerequisites" feature of make to prevent writes
of files into the directories generating re-builds, as suggested in the
GNU make Manual (Version 4.1 September 2014).

Change-Id: Ic9af475831063c7fe6f8bccffef184d79e799419

1 files changed, 23 insertions, 13 deletions

diff --git a/make_helpers/build_macros.mk b/make_helpers/build_macros.mk
index 5a67c4c1..f82ba534 100644
--- a/make_helpers/build_macros.mk
+++ b/make_helpers/build_macros.mk
@@ -210,10 +210,8 @@ $(OBJ): $(2)
 	@echo "  CC      $$<"
 	$$(Q)$$(CC) $$(CFLAGS) -D$(IMAGE) -c $$< -o $$@
 
-
-$(PREREQUISITES): $(2)
+$(PREREQUISITES): $(2) | bl$(3)_dirs
 	@echo "  DEPS    $$@"
-	@mkdir -p $(1)
 	$$(Q)$$(CC) $$(CFLAGS) -M -MT $(OBJ) -MF $$@ $$<
 
 ifdef IS_ANYTHING_TO_BUILD
@@ -237,9 +235,8 @@ $(OBJ): $(2)
 	@echo "  AS      $$<"
 	$$(Q)$$(AS) $$(ASFLAGS) -D$(IMAGE) -c $$< -o $$@
 
-$(PREREQUISITES): $(2)
+$(PREREQUISITES): $(2) | bl$(3)_dirs
 	@echo "  DEPS    $$@"
-	@mkdir -p $(1)
 	$$(Q)$$(AS) $$(ASFLAGS) -M -MT $(OBJ) -MF $$@ $$<
 
 ifdef IS_ANYTHING_TO_BUILD
@@ -260,9 +257,8 @@ $(1): $(2)
 	@echo "  PP      $$<"
 	$$(Q)$$(AS) $$(ASFLAGS) -P -E -D__LINKER__ -o $$@ $$<
 
-$(PREREQUISITES): $(2)
+$(PREREQUISITES): $(2) | $(dir ${1})
 	@echo "  DEPS    $$@"
-	@mkdir -p $$(dir $$@)
 	$$(Q)$$(AS) $$(ASFLAGS) -M -MT $(1) -MF $$@ $$<
 
 ifdef IS_ANYTHING_TO_BUILD
@@ -327,14 +323,28 @@ define MAKE_BL
         $(eval DUMP       := $(call IMG_DUMP,$(1)))
         $(eval BIN        := $(call IMG_BIN,$(1)))
         $(eval BL_LINKERFILE := $(BL$(call uppercase,$(1))_LINKERFILE))
+        # We use sort only to get a list of unique object directory names.
+        # ordering is not relevant but sort removes duplicates.
+        $(eval TEMP_OBJ_DIRS := $(sort $(BUILD_DIR)/ $(dir ${OBJS})))
+        # The $(dir ) function leaves a trailing / on the directory names
+        # We append a . then strip /. from each, to remove the trailing / characters
+        # This gives names suitable for use as make rule targets.
+        $(eval OBJ_DIRS   := $(subst /.,,$(addsuffix .,$(TEMP_OBJ_DIRS))))
+
+# Create generators for object directory structure
+
+$(eval $(foreach objd,${OBJ_DIRS},$(call MAKE_PREREQ_DIR,${objd},)))
+
+.PHONY : bl${1}_dirs
 
-        $(eval $(call MAKE_OBJS,$(BUILD_DIR),$(SOURCES),$(1)))
-        $(eval $(call MAKE_LD,$(LINKERFILE),$(BL_LINKERFILE)))
+# We use order-only prerequisites to ensure that directories are created,
+# but do not cause re-builds every time a file is written.
+bl${1}_dirs: | ${OBJ_DIRS}
 
-$(BUILD_DIR):
-	$$(Q)mkdir -p "$$@"
+$(eval $(call MAKE_OBJS,$(BUILD_DIR),$(SOURCES),$(1)))
+$(eval $(call MAKE_LD,$(LINKERFILE),$(BL_LINKERFILE)))
 
-$(ELF): $(OBJS) $(LINKERFILE)
+$(ELF): $(OBJS) $(LINKERFILE) | bl$(1)_dirs
 	@echo "  LD      $$@"
 	@echo 'const char build_message[] = "Built : "$(BUILD_MESSAGE_TIMESTAMP); \
 	       const char version_string[] = "${VERSION_STRING}";' | \
@@ -354,7 +364,7 @@ $(BIN): $(ELF)
 	@echo
 
 .PHONY: bl$(1)
-bl$(1): $(BUILD_DIR) $(BIN) $(DUMP)
+bl$(1): $(BIN) $(DUMP)
 
 all: bl$(1)