Use ThinLTO instead of full LTO
Use ThinLTO instead of full LTO

It feels like the build time increase caused by enabling LTO is
significant. ThinLTO is significant faster than full LTO, but the
performance loss should be minimal. I ran cluster test and did not
notice significant perf difference.

Closes: #2285
Approved by: metajack

libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core