Support setting the RELSTR

To build identical binaries the RELSTR must be identical, too.

.travis.yml

@@ -5,6 +5,9 @@ before_script:
   - WGET="travis_retry wget --continue --tries=20 --waitretry=10 --retry-connrefused --no-dns-cache --timeout 300"
   - sudo apt-get -qq update
 
+  ## Support building the same binary as on CI
+  - echo -n "Contiki will be compiled with RELSTR=" ; git --git-dir .git describe --tags --always
+
   ## Install msp430 toolchain
   - sudo apt-get -qq install lib32z1
   - $WGET http://adamdunkels.github.io/contiki-fork/mspgcc-4.7.0-compiled.tar.bz2 &&

Makefile.include

@@ -152,8 +152,10 @@ CFLAGS += ${addprefix -I,$(SOURCEDIRS) $(CONTIKI)}
 
 ### Check for a git repo and pass version if found
 ### git.exe in Windows cmd shells may require no stderr redirection
-#RELSTR=${shell git describe --tags}
-RELSTR:=${shell git --git-dir ${CONTIKI}/.git describe --tags 2>/dev/null}
+ifndef RELSTR
+RELSTR:=${shell git --git-dir ${CONTIKI}/.git describe --tags --always}
+endif
+
 ifneq ($(RELSTR),)
 CFLAGS += -DCONTIKI_VERSION_STRING=\"Contiki-$(RELSTR)\"
 endif