cargo: fix build issue
Using ubuntu 20.04, the build was failing with version cargo 0.47/ rustc 1.47. Following this discussion: https://github.com/rust-lang/cargo/issues/9340 it appears that 0.52 is the minimum version.
Using ubuntu 20.04, the build was failing with version cargo 0.47/ rustc 1.47. Following this discussion: https://github.com/rust-lang/cargo/issues/9340 it appears that 0.52 is the minimum version.