Change directory-specific CFLAGS to use full path

Previously, a specific file or directory could be compiled with custom
CFLAGS by adding a Makefile variable such as:
  CFLAGS_dlmalloc.o = <custom flags for common/dlmalloc.c>
or
  CFLAGS_lib = <custom flags for lib directory>

This method breaks down once multiple files or directories share the
same path.  Eg FLAGS_fileA = <custom flags> would incorrectly result in
both dir1/fileA.c and dir2/fileA.c being compiled with <custom flags>.

This change allows finer grained control which we need once we move
lib_$ARCH to arch/$ARCH/lib/ and lib_generic/ to lib/.  Without this
change all lib/ directories would share the same custom CFLAGS.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>

config.mk

@@ -236,16 +236,21 @@ export	TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS CPPFLAGS CFLAGS AFLAGS
 #########################################################################
 
 # Allow boards to use custom optimize flags on a per dir/file basis
-BCURDIR := $(notdir $(CURDIR))
+BCURDIR = $(subst $(SRCTREE)/,,$(CURDIR:$(obj)%=%))
 $(obj)%.s:	%.S
-	$(CPP) $(AFLAGS) $(AFLAGS_$(@F)) $(AFLAGS_$(BCURDIR)) -o $@ $<
+	$(CPP) $(AFLAGS) $(AFLAGS_$(BCURDIR)/$(@F)) $(AFLAGS_$(BCURDIR)) \
+		-o $@ $<
 $(obj)%.o:	%.S
-	$(CC)  $(AFLAGS) $(AFLAGS_$(@F)) $(AFLAGS_$(BCURDIR)) -o $@ $< -c
+	$(CC)  $(AFLAGS) $(AFLAGS_$(BCURDIR)/$(@F)) $(AFLAGS_$(BCURDIR)) \
+		-o $@ $< -c
 $(obj)%.o:	%.c
-	$(CC)  $(CFLAGS) $(CFLAGS_$(@F)) $(CFLAGS_$(BCURDIR)) -o $@ $< -c
+	$(CC)  $(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR)) \
+		-o $@ $< -c
 $(obj)%.i:	%.c
-	$(CPP) $(CFLAGS) $(CFLAGS_$(@F)) $(CFLAGS_$(BCURDIR)) -o $@ $< -c
+	$(CPP) $(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR)) \
+		-o $@ $< -c
 $(obj)%.s:	%.c
-	$(CC)  $(CFLAGS) $(CFLAGS_$(@F)) $(CFLAGS_$(BCURDIR)) -o $@ $< -c -S
+	$(CC)  $(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR)) \
+		-o $@ $< -c -S
 
 #########################################################################