Merge pull request #1499 from LudwigOrtmann/riot-version-fail

make: improve failing RIOT_VERSION

Makefile.include

@@ -65,7 +65,7 @@ include $(RIOTBASE)/Makefile.cflags
 
 # make the RIOT version available to the program
 ifeq ($(origin RIOT_VERSION), undefined)
-  GIT_STRING := $(shell git describe --always --abbrev=4 --dirty=-`hostname`)
+  GIT_STRING := $(shell git describe --always --abbrev=4 --dirty=-`hostname` 2> /dev/null)
   ifneq (,$(GIT_STRING))
     GIT_BRANCH := $(shell git rev-parse --abbrev-ref HEAD)
     ifeq ($(strip $(GIT_BRANCH)),master)
@@ -74,7 +74,7 @@ ifeq ($(origin RIOT_VERSION), undefined)
       RIOT_VERSION := $(GIT_STRING)-$(GIT_BRANCH)
     endif
   else
-    RIOT_VERSION := UNKNOWN
+    RIOT_VERSION := UNKNOWN (builddir: $(RIOTBASE))
   endif
 endif
 export CFLAGS += -DRIOT_VERSION='"$(RIOT_VERSION)"'