fdt: Ensure that libfdt_env.h comes from U-Boot

When building host utilities, we include libfdt.h from the host, not from
U-Boot. This in turn brings in libfdt_env.h from the host, which can mess
up the types and cause a build failure, depending on the host environment.
To fix this, force inclusion of U-Boot's libfdt_env.h so that the types
are correct.

Another way to fix this is to use -nostdinc and -idirafter to ensure that
system includes are included after U-Boot ones. Unfortunately this means
that U-Boot's errno.h gets included instead of the system one. This in
turn requires a hack to errno.h to redirect things, so all in all the
solution in this patch is probably cleaner.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/Makefile

@@ -164,7 +164,8 @@ NOPEDOBJS := $(addprefix $(obj),$(NOPED_OBJ_FILES-y))
 # Use native tools and options
 # Define __KERNEL_STRICT_NAMES to prevent typedef overlaps
 #
-HOSTCPPFLAGS =	-idirafter $(SRCTREE)/include \
+HOSTCPPFLAGS =	-include $(SRCTREE)/include/libfdt_env.h \
+		-idirafter $(SRCTREE)/include \
 		-idirafter $(OBJTREE)/include2 \
 		-idirafter $(OBJTREE)/include \
 	        -I $(SRCTREE)/lib/libfdt \