stage1/diagexec: add working directory option
stage1/diagexec: add working directory option

New diagexec calling convention:
diagexec /path/to/chroot /desired/cwd/within/root cmd_within_root [ARGS [...]]

squaremo/rkt,eyakubovich/rkt,kinvolk/rkt,Wilybald/rkt,monstermunchkin/rkt,achanda/rkt,liubq919/rkt,klizhentas/rkt,yifan-gu/rocket,MabinGo/rkt,rkt/rkt,mattthias/pkg-rkt,shobhit85/rkt,jasonchaffee/rkt,squeed/rkt,markllama/rkt,crawford/rkt,alban/rkt,euank/rkt,dgonyeo/rkt,smarvin/rkt,sgotti/rkt,kbrwn/rkt,robszumski/rocket,chrisseto/rkt,liugenping/rkt,squaremo/rkt,sstabellini/rkt,yifan-gu/rkt,lsm5/rkt,ramitsurana/rkt,rhvgoyal/rkt,kbrwn/rkt,wparad/rkt,MabinGo/rkt,crawford/rkt,maquanyi/rkt,alexhersh/rkt,squaremo/rkt,s-urbaniak/rkt,monstermunchkin/rkt,liugenping/rkt,jjlakis/rkt,intfrr/rkt,ChengTiesheng/rkt,tv42/rkt,yifan-gu/rkt,jzelinskie/rkt,lee212/rkt,michelangelo13/rkt,tixxdz/rkt,clearlinux/rkt,alban/rkt,akshaykarle/rkt,michelangelo13/rkt,kinvolk/rkt,jakon89/rkt,mike1729/rkt,iaguis/rkt,sgotti/rkt,mike1729/rkt,mike1729/rkt,shobhit85/rkt,ramitsurana/rkt,luebken/rkt,intfrr/rkt,tv42/rkt,krnowak/rkt,tmrts/rkt,klizhentas/rkt,cab105/rkt,intfrr/rkt,tv42/rkt,yifan-gu/rkt,sstabellini/rkt,fdserr/rkt,chrisseto/rkt,tmrts/rkt,bsmr-go/rkt,blixtra/rkt,markllama/rkt,Yhgenomics/rkt,mattthias/pkg-rkt,rkt/rkt,tixxdz/rkt,rhvgoyal/rkt,rkt/rkt,intelsdi-x/rkt,coreos/rkt,ramitsurana05/rkt,dalanlan/rkt,kbrwn/rkt,iankronquist/rkt,lucasallan/rkt,shtouff/rkt,shtouff/rkt,jonboulle/rkt,coreos/rkt,markllama/rkt,cab105/rkt,maquanyi/rkt,jonboulle/rkt,Wilybald/rkt,endocode/rkt,dalanlan/rkt,luebken/rkt,Shashwatsh/rkt,wparad/rkt,tixxdz/rkt,lucasallan/rkt,joshix/rkt,robszumski/rocket,xnox/rkt,xnox/rkt,Shashwatsh/rkt,euank/rkt,MattDees/rkt,ybubnov/rkt,akshaykarle/rkt,liubq919/rkt,marineam/rkt,blixtra/rkt,squeed/rkt,yifan-gu/rocket,mjg59/rkt,clearlinux/rkt,ybubnov/rkt,sinfomicien/rkt,endocode/rkt,linki/rkt,lsm5/rkt,s-urbaniak/rkt,jjlakis/rkt,lucasallan/rkt,matthaias/rkt,maquanyi/rkt,iaguis/rkt,sinfomicien/rkt,shtouff/rkt,ramitsurana/rkt,MattDees/rkt,jasonchaffee/rkt,akshaykarle/rkt,cab105/rkt,ChengTiesheng/rkt,mattthias/pkg-rkt,intelsdi-x/rkt,dgonyeo/rkt,krnowak/rkt,il9ue/rkt,sinfomicien/rkt,linki/rkt,lee212/rkt,monstermunchkin/rkt,fdserr/rkt,joshix/rkt,Yhgenomics/rkt,marineam/rkt,smarvin/rkt,euank/rkt,luebken/rkt,robszumski/rocket,rot26/rkt,jjlakis/rkt,joshix/rkt,achanda/rkt,lucasallan/rkt,alexhersh/rkt,joshix/rkt,sstabellini/rkt,dalanlan/rkt,jzelinskie/rkt,Wilybald/rkt,smarvin/rkt,marineam/rkt,achanda/rkt,intelsdi-x/rkt,rot26/rkt,michelangelo13/rkt,MattDees/rkt,alban/rkt,adfernandes/rkt,endocode/rkt,jasonchaffee/rkt,krnowak/rkt,shobhit85/rkt,lee212/rkt,jakon89/rkt,rot26/rkt,MabinGo/rkt,chrisseto/rkt,rhvgoyal/rkt,ramitsurana05/rkt,iaguis/rkt,kinvolk/rkt,ybubnov/rkt,Shashwatsh/rkt,clearlinux/rkt,nhlfr/rkt,jzelinskie/rkt,eyakubovich/rkt,wparad/rkt,Yhgenomics/rkt,iankronquist/rkt,linki/rkt,sgotti/rkt,matthaias/rkt,liugenping/rkt,squeed/rkt,s-urbaniak/rkt,il9ue/rkt,fdserr/rkt,bsmr-go/rkt,dgonyeo/rkt,alexhersh/rkt,klizhentas/rkt,nhlfr/rkt,lsm5/rkt,nhlfr/rkt,mjg59/rkt,liubq919/rkt,tmrts/rkt,adfernandes/rkt,ChengTiesheng/rkt,adfernandes/rkt,bsmr-go/rkt,coreos/rkt,eyakubovich/rkt,kinvolk/rkt,iankronquist/rkt,blixtra/rkt,il9ue/rkt,yifan-gu/rocket,matthaias/rkt,ramitsurana05/rkt,xnox/rkt,jakon89/rkt,jonboulle/rkt,crawford/rkt,mjg59/rkt,rkt/rkt,Wilybald/rkt