Android: Enable arm64-v8a export by default
Android: Enable arm64-v8a export by default

From August 1, 2019, Google Play requires that all new apps and app updates
include 64-bit versions, so we enable ARM64 by default.

IINM support for x86 and x86_64 is still be optional, so not enabling them
out of the box.

Part of #25030.

godotengine/godot,okamstudio/godot,honix/godot,Valentactive/godot,sanikoyes/godot,DmitriySalnikov/godot,Shockblast/godot,vkbsb/godot,Shockblast/godot,guilhermefelipecgs/godot,josempans/godot,akien-mga/godot,MarianoGnu/godot,sanikoyes/godot,okamstudio/godot,ex/godot,honix/godot,Valentactive/godot,godotengine/godot,ZuBsPaCe/godot,josempans/godot,Paulloz/godot,DmitriySalnikov/godot,guilhermefelipecgs/godot,firefly2442/godot,ex/godot,Zylann/godot,Valentactive/godot,MarianoGnu/godot,MarianoGnu/godot,vkbsb/godot,akien-mga/godot,Valentactive/godot,firefly2442/godot,Zylann/godot,ex/godot,BastiaanOlij/godot,vnen/godot,Faless/godot,MarianoGnu/godot,Zylann/godot,okamstudio/godot,BastiaanOlij/godot,firefly2442/godot,godotengine/godot,ex/godot,Faless/godot,okamstudio/godot,vkbsb/godot,BastiaanOlij/godot,guilhermefelipecgs/godot,pkowal1982/godot,ZuBsPaCe/godot,Shockblast/godot,Paulloz/godot,vnen/godot,DmitriySalnikov/godot,josempans/godot,Faless/godot,okamstudio/godot,DmitriySalnikov/godot,josempans/godot,Zylann/godot,guilhermefelipecgs/godot,okamstudio/godot,Valentactive/godot,Faless/godot,Paulloz/godot,DmitriySalnikov/godot,firefly2442/godot,ZuBsPaCe/godot,firefly2442/godot,guilhermefelipecgs/godot,pkowal1982/godot,Faless/godot,Zylann/godot,MarianoGnu/godot,Faless/godot,ZuBsPaCe/godot,ZuBsPaCe/godot,vnen/godot,honix/godot,akien-mga/godot,josempans/godot,sanikoyes/godot,okamstudio/godot,josempans/godot,Zylann/godot,ex/godot,Shockblast/godot,Faless/godot,akien-mga/godot,vnen/godot,josempans/godot,sanikoyes/godot,sanikoyes/godot,honix/godot,Zylann/godot,groud/godot,guilhermefelipecgs/godot,ZuBsPaCe/godot,pkowal1982/godot,sanikoyes/godot,ex/godot,ZuBsPaCe/godot,akien-mga/godot,MarianoGnu/godot,sanikoyes/godot,ex/godot,pkowal1982/godot,godotengine/godot,Valentactive/godot,pkowal1982/godot,groud/godot,vkbsb/godot,groud/godot,BastiaanOlij/godot,Paulloz/godot,godotengine/godot,honix/godot,Valentactive/godot,guilhermefelipecgs/godot,okamstudio/godot,Zylann/godot,Paulloz/godot,BastiaanOlij/godot,BastiaanOlij/godot,BastiaanOlij/godot,firefly2442/godot,firefly2442/godot,Shockblast/godot,MarianoGnu/godot,firefly2442/godot,godotengine/godot,groud/godot,vkbsb/godot,Paulloz/godot,ZuBsPaCe/godot,godotengine/godot,vnen/godot,honix/godot,BastiaanOlij/godot,pkowal1982/godot,josempans/godot,sanikoyes/godot,Faless/godot,Shockblast/godot,groud/godot,vkbsb/godot,vkbsb/godot,godotengine/godot,pkowal1982/godot,MarianoGnu/godot,vnen/godot,DmitriySalnikov/godot,okamstudio/godot,Paulloz/godot,Valentactive/godot,vnen/godot,akien-mga/godot,vnen/godot,okamstudio/godot,groud/godot,ex/godot,akien-mga/godot,Shockblast/godot,akien-mga/godot,guilhermefelipecgs/godot,Shockblast/godot,DmitriySalnikov/godot,vkbsb/godot,pkowal1982/godot