Unable to find PostgreSQL client library

Setting up a Rails + Postgres app but deployment is failing due to an "Unable to find PostgreSQL client library" error.

```
#11 61.22 Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
#11 61.22
#11 61.22 current directory: /usr/local/bundle/ruby/3.1.0/gems/pg-1.5.4/ext
#11 61.22 /usr/local/bin/ruby -I /usr/local/lib/ruby/3.1.0 extconf.rb
#11 61.22 Calling libpq with GVL unlocked
#11 61.22 checking for pg_config... no
#11 61.22 checking for libpq per pkg-config... no
#11 61.22 Using libpq from
#11 61.22 checking for libpq-fe.h... no
#11 61.22 Can't find the 'libpq-fe.h header
#11 61.22 **
#11 61.22 Unable to find PostgreSQL client library.
#11 61.22
#11 61.22 Please install libpq or postgresql client package like so:
#11 61.22 sudo apt install libpq-dev
#11 61.22 sudo yum install postgresql-devel
#11 61.22 sudo zypper in postgresql-devel
#11 61.22 sudo pacman -S postgresql-libs
#11 61.22
#11 61.22 or try again with:
#11 61.22 gem install pg -- --with-pg-config=/path/to/pg_config
#11 61.22
#11 61.22 or set library paths manually with:
#11 61.22 gem install pg -- --with-pg-include=/path/to/libpq-fe.h/
#11 61.22 --with-pg-lib=/path/to/libpq.so/
#11 61.22
#11 61.22 ** extconf.rb failed ***

Project ID: f59727c4-9101-4b02-8fa6-d9109efcd3bd

untested, but try adding this as a nixpacks.toml to your project

[phases.setup]
  aptPkgs = ['...', 'libpq-dev']