JS target: use -Os instead of -O3
JS target: use -Os instead of -O3

Performance is roughly the same, but output is noticeably smaller

rustyhorde/libsodium,pmienk/libsodium,Payshares/libsodium,rustyhorde/libsodium,rustyhorde/libsodium,Payshares/libsodium,pmienk/libsodium,Payshares/libsodium,rustyhorde/libsodium,pmienk/libsodium