chore(deps): update external/libzmq digest to 64db7d2 #82

Job	Run time
lib_android (monero)	25m 52s
lib_darwin (monero)	13m 42s
lib_android (wownero)	25m 34s
lib_darwin (wownero)	13m 33s
lib_linux (monero)	2m 53s
ios build (monero)	10m 22s
macos build (monero)	3m 30s
lib_linux (wownero)	2m 29s
ios build (wownero)	9m 56s
macos build (wownero)	3m 22s
lib_mingw (monero)	3m 30s
lib_sailfishos_aarch64 (monero)	3m 51s
lib_mingw (wownero)	3m 40s
lib_sailfishos_i486 (monero)	2m 10s
lib_sailfishos_aarch64 (wownero)	3m 36s
lib_sailfishos_i486 (wownero)	2m 31s
wallet_cake_android	20m 43s
wallet_xmruw_android (monero)	6m 44s
wallet_xmruw_android (wownero)	6m 39s
comment on pr	4s
	2h 44m 41s

Provide feedback