releng: always use gradle wrapper
releng: always use gradle wrapper

Otherwise different developers might have different build output.
matej116/cgeo,ThibaultR/cgeo,ThibaultR/cgeo,superspindel/cgeo,kumy/cgeo,pstorch/cgeo,cgeo/cgeo,kumy/cgeo,cgeo/cgeo,SammysHP/cgeo,S-Bartfast/cgeo,tobiasge/cgeo,rsudev/c-geo-opensource,auricgoldfinger/cgeo,S-Bartfast/cgeo,samueltardieu/cgeo,matej116/cgeo,kumy/cgeo,pstorch/cgeo,cgeo/cgeo,superspindel/cgeo,samueltardieu/cgeo,ThibaultR/cgeo,mucek4/cgeo,tobiasge/cgeo,Bananeweizen/cgeo,mucek4/cgeo,rsudev/c-geo-opensource,SammysHP/cgeo,superspindel/cgeo,pstorch/cgeo,auricgoldfinger/cgeo,matej116/cgeo,rsudev/c-geo-opensource,mucek4/cgeo,Bananeweizen/cgeo,SammysHP/cgeo,cgeo/cgeo,Bananeweizen/cgeo,samueltardieu/cgeo,tobiasge/cgeo,S-Bartfast/cgeo,auricgoldfinger/cgeo