Specify build dependencies

[bryanasdev000]

Hello there!

I think it makes sense to specify in README.md the dependencies needed to compile the package in the RHEL and Debian families. The specific version would also be cool, since CentOS specifically requires the use of third party repos to have updated versions of LLVM, Clang and GCC.

Note: I specifically use version 11 of PostgreSQL because of TimescaleDB.

For now I am currently using the following packages for Debian based:

• git
• make
• gcc
• libpq-dev
• postgresql-server-dev-11

and on Red Hat based systems:

CentOS 7 (need epel-release and centos-release-scl):

• centos-release-scl
• epel-release
• git
• make
• gcc
• libpqxx-devel
• postgresql11-devel
• devtoolset-7
• llvm-toolset-7

On CentOS 8 (need only epel-release):

• git
• make
• gcc
• libpqxx-devel
• postgresql11-devel
• clang
• redhat-rpm-config
• ccache
• llvm

If every1 agree I can do a PR with the content above.