message: move musl and libcxx submodules to https urls
diff: url = https://github.com/EOSIO/genesis.git
  [submodule "contracts/musl/upstream"]
  path = contracts/musl/upstream
  - url = git@github.com:EOSIO/musl.git
  + url = https://github.com/EOSIO/musl.git
  branch = eosio
  [submodule "contracts/libc++/upstream"]
  path = contracts/libc++/upstream
  - url = git@github.com:EOSIO/libcxx.git
  + url = https://github.com/EOSIO/libcxx.git
  branch = eosio
  