build: Cleanups in find-so-deps.mk
build: Cleanups in find-so-deps.mk

Rename a variable. Later, we will copy libraries to another directory
named "libs", so we will be able to generate a filelist. To avoid a
confusion with a future variable holding a name of a temporary
libraries directory, we rename the variable holding paths for the
LD_LIBRARY_PATH environment variable.

Also, add a toplevel stamp, which for now depends on another stamp, so
it looks redundant. But later it will depend on more stuff, like
generated clean files.

This is a preparatory commit for adding filelist generation.

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