Don't pass -I<platform-dir> twice
We currently pass this CFLAG twice. For example:
```
$ make TARGET=zoul V=1
arm-none-eabi-gcc [...] -I. -I../../arch/platform/zoul/. [...] -I../../arch/platform/zoul/
```
This commit fixes this behaviour
@@ -283,7 +283,7 @@ CONTIKI_CPU_DIRS_CONCAT = ${addprefix $(CONTIKI_CPU)/, \
CONTIKI_ARCH_DIRS = ${addprefix $(CONTIKI)/, arch}
SOURCEDIRS = . $(PROJECTDIRS) $(CONTIKI_TARGET_DIRS_CONCAT) $(CONTIKI_ARCH_DIRS) \
- $(CONTIKI_CPU_DIRS_CONCAT) $(CONTIKIDIRS) $(MODULEDIRS) $(EXTERNALDIRS) ${dir $(target_makefile)}
+ $(CONTIKI_CPU_DIRS_CONCAT) $(CONTIKIDIRS) $(MODULEDIRS) $(EXTERNALDIRS)
vpath %.c $(SOURCEDIRS)
vpath %.S $(SOURCEDIRS)
