Reproducibility issue of the snowflake osx64 build

The build of Snowflake for MacOS is often producing the same result, but not always.

Arthur has been rebuilding Snowflake 8 times, with 4 different results: https://gist.github.com/arthuredelstein/73860df088c565ea0b2ca6eef586063a

fish script:

for x in (seq 8)
    rm out/snowflake/snowflake-6077141f4aff-osx-x86_64-3b578d.tar.gz
    ./rbm/rbm build snowflake  --target alpha --target torbrowser-osx-x86_64
    tar xvf out/snowflake/snowflake-6077141f4aff-osx-x86_64-3b578d.tar.gz
    echo (sha256sum ./Contents/MacOS/Tor/PluggableTransports/snowflake-client
end

Results:

b060b42cfd0c8fb2781dbb0fd45d42804dbb414473fec0597d9c2fb7d6d12aa8  ./Contents/MacOS/Tor/PluggableTransports/snowflake-client
1ee0dd2a0b228988e22c663d62b696b23a6ac48dc742a57dfa8f854aa3992bc3  ./Contents/MacOS/Tor/PluggableTransports/snowflake-client
22557c38d913e478e480dd3581efc00019fe2989c4273d9207f1719c34b6e399  ./Contents/MacOS/Tor/PluggableTransports/snowflake-client
22557c38d913e478e480dd3581efc00019fe2989c4273d9207f1719c34b6e399  ./Contents/MacOS/Tor/PluggableTransports/snowflake-client
1ee0dd2a0b228988e22c663d62b696b23a6ac48dc742a57dfa8f854aa3992bc3  ./Contents/MacOS/Tor/PluggableTransports/snowflake-client
1ee0dd2a0b228988e22c663d62b696b23a6ac48dc742a57dfa8f854aa3992bc3  ./Contents/MacOS/Tor/PluggableTransports/snowflake-client
1ee0dd2a0b228988e22c663d62b696b23a6ac48dc742a57dfa8f854aa3992bc3  ./Contents/MacOS/Tor/PluggableTransports/snowflake-client
6d008bc7d29e8543608491b67d4b11da7bd6589741d9f52ac5fd50dd39d84f29  ./Contents/MacOS/Tor/PluggableTransports/snowflake-client