Remove getenv calls before libc startup

[vtikoo]

lkl_start_init is using getenv fairly early in the initialization sequence. Which is requiring an early call to __init_libc.

According to @davidchisnall - When we parse the environment variables from the config file, we should pull the SGX-LKL ones into globals and skip them, then we wouldn't need that extra complexity here. From - https://github.com/lsds/sgx-lkl-musl/pull/18#discussion_r469807014