build: ignore errors if we're not in a git repo
build: ignore errors if we're not in a git repo

If we didn't build from a git repo, the version will be just the rkt
version, without any hash (e.g. "rkt 0.7.0+git" or "rkt 0.7.0" if we
exported the code from tag 0.7.0)

dalanlan/rkt,iankronquist/rkt,kinvolk/rkt,intfrr/rkt,tv42/rkt,lee212/rkt,MattDees/rkt,liugenping/rkt,jjlakis/rkt,intfrr/rkt,mjg59/rkt,cab105/rkt,jjlakis/rkt,shobhit85/rkt,matthaias/rkt,akshaykarle/rkt,il9ue/rkt,lucasallan/rkt,matthaias/rkt,achanda/rkt,Wilybald/rkt,dgonyeo/rkt,blixtra/rkt,rkt/rkt,sstabellini/rkt,nhlfr/rkt,Wilybald/rkt,Wilybald/rkt,yifan-gu/rocket,lucasallan/rkt,jakon89/rkt,coreos/rkt,jasonchaffee/rkt,liugenping/rkt,liubq919/rkt,markllama/rkt,shobhit85/rkt,chrisseto/rkt,euank/rkt,mike1729/rkt,Shashwatsh/rkt,euank/rkt,adfernandes/rkt,jasonchaffee/rkt,jakon89/rkt,blixtra/rkt,tmrts/rkt,sgotti/rkt,MattDees/rkt,marineam/rkt,sstabellini/rkt,jjlakis/rkt,endocode/rkt,rkt/rkt,jonboulle/rkt,tmrts/rkt,s-urbaniak/rkt,sinfomicien/rkt,mjg59/rkt,lee212/rkt,markllama/rkt,mjg59/rkt,jasonchaffee/rkt,squeed/rkt,joshix/rkt,kinvolk/rkt,akshaykarle/rkt,blixtra/rkt,iaguis/rkt,dalanlan/rkt,kbrwn/rkt,joshix/rkt,endocode/rkt,ybubnov/rkt,matthaias/rkt,joshix/rkt,monstermunchkin/rkt,nhlfr/rkt,rkt/rkt,monstermunchkin/rkt,liubq919/rkt,iankronquist/rkt,dgonyeo/rkt,krnowak/rkt,akshaykarle/rkt,s-urbaniak/rkt,jonboulle/rkt,alexhersh/rkt,markllama/rkt,squeed/rkt,chrisseto/rkt,intelsdi-x/rkt,luebken/rkt,ybubnov/rkt,linki/rkt,cab105/rkt,alexhersh/rkt,squeed/rkt,luebken/rkt,euank/rkt,iankronquist/rkt,kbrwn/rkt,sgotti/rkt,intelsdi-x/rkt,smarvin/rkt,sgotti/rkt,sstabellini/rkt,dalanlan/rkt,linki/rkt,Yhgenomics/rkt,linki/rkt,coreos/rkt,adfernandes/rkt,joshix/rkt,lee212/rkt,MattDees/rkt,jzelinskie/rkt,jakon89/rkt,cab105/rkt,kinvolk/rkt,sinfomicien/rkt,mike1729/rkt,jzelinskie/rkt,rkt/rkt,ybubnov/rkt,liugenping/rkt,adfernandes/rkt,coreos/rkt,iaguis/rkt,intfrr/rkt,marineam/rkt,smarvin/rkt,intelsdi-x/rkt,yifan-gu/rocket,il9ue/rkt,luebken/rkt,tmrts/rkt,sinfomicien/rkt,marineam/rkt,Yhgenomics/rkt,achanda/rkt,shobhit85/rkt,alban/rkt,monstermunchkin/rkt,iaguis/rkt,mike1729/rkt,Shashwatsh/rkt,jzelinskie/rkt,liubq919/rkt,alexhersh/rkt,lucasallan/rkt,yifan-gu/rkt,lucasallan/rkt,jonboulle/rkt,tv42/rkt,yifan-gu/rocket,smarvin/rkt,il9ue/rkt,krnowak/rkt,yifan-gu/rkt,dgonyeo/rkt,yifan-gu/rkt,alban/rkt,kinvolk/rkt,krnowak/rkt,s-urbaniak/rkt,endocode/rkt,nhlfr/rkt,Shashwatsh/rkt,tv42/rkt,Wilybald/rkt,kbrwn/rkt,alban/rkt,chrisseto/rkt,achanda/rkt,Yhgenomics/rkt