Fix build issues on latest ubuntu #57

Job	Run time
lib_android (monero)	25m 25s
lib_android (wownero)	25m 34s
lib_darwin (monero)	14m 5s
lib_darwin (wownero)	13m 35s
ios build (monero)	11m 53s
ios build (wownero)	10m 24s
lib_linux (monero)	6m 50s
lib_linux (wownero)	6m 51s
macos build (monero)	3m 7s
macos build (wownero)	3m 11s
lib_mingw (monero)	4m 0s
lib_mingw (wownero)	4m 28s
lib_sailfishos_aarch64 (monero)	3m 25s
lib_sailfishos_aarch64 (wownero)	3m 25s
lib_sailfishos_i486 (monero)	3m 15s
lib_sailfishos_i486 (wownero)	2m 46s
wallet_cake_android	22m 27s
wallet_xmruw_android (monero)	7m 16s
wallet_xmruw_android (wownero)	7m 27s
comment on pr	5s
	2h 59m 29s

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