Manual install luarocks

[rustprooflabs]

Issue with older luarocks installed by apt install luarocks. Resulted in v2.4.0 (circa 2016?) installed. Failure from still using the unsecure git:// protocol. Using method documented in #218 hoping it fixes the issue.

https://github.com/rustprooflabs/pgosm-flex/runs/5684687464?check_suite_focus=true

 > [ 5/11] RUN luarocks install luasql-postgres PGSQL_INCDIR=/usr/include/postgresql/:
#9 1.124 Installing https://luarocks.org/luasql-postgres-2.6.0-1.rockspec
#9 1.438 Cloning into 'luasql'...
#9 1.545 fatal: remote error: 
#9 1.545   The unauthenticated git protocol on port 9418 is no longer supported.
#9 1.545 Please see https://github.blog/2021-09-01-improving-git-protocol-security-github/ for more information.
#9 1.547 
#9 1.547 Error: Failed cloning git repository.
------
error: failed to solve: executor failed running [/bin/sh -c luarocks install luasql-postgres PGSQL_INCDIR=/usr/include/postgresql/]: exit code: 1
Error: buildx failed with: error: failed to solve: executor failed running [/bin/sh -c luarocks install luasql-postgres PGSQL_INCDIR=/usr/include/postgresql/]: exit code: 1