Setup a CI

[weiznich]

We should setup a CI job for this repository to check if everything builds correctly.

We should test the following cases listed in our Readme:

• First it will look for an environment variable in the format of PQ_LIB_DIR_{TARGET} where {TARGET} gets replaced by the Target environment variable set for cross-compilation
• Second, if the environment variable PQ_LIB_DIR is set, it will use its value
• If the environment variable isn't set, it tries to use pkg-config to locate it. All the config options, such as PKG_CONFIG_ALLOW_CROSS, PKG_CONFIG_ALL_STATIC etc., of the crate pkg-config apply.
• Then, for MSVC ABI builds the build script will attempt use the library from a vcpkg installation if there is one available. You may need to set VCPKG_ROOT (or run vcpkg integrate install), set VCPKGRS_DYNAMIC=1, and run vcpkg install libpq:x64-windows. See the documentation for the vcpkg crate for more.
• If it still can't locate the library, it will invoke the Postgres command pg_config --libdir

Optimally this should be tested for windows, macos + linux.

[chadelofson]

I can work on a Github Action for that.

[weiznich]

That would be great ❤️

Diesel's CI configuration is likely a good starting point for how libpq can be setup on the different operating systems. Otherwise please just reach out if you have problems somewhere.

[chadelofson]

I am using the Diesel CI config for the starting point. Do you need to have this tested on the Stable, Beta and Nightly versions of Rust?

[weiznich]

Just testing on stable would be fine.

[chadelofson]

• First it will look for an environment variable in the format of PQ_LIB_DIR_{TARGET} where {TARGET} gets replaced by the Target environment variable set for cross-compilation
• Second, if the environment variable PQ_LIB_DIR is set, it will use its value
• If the environment variable isn't set, it tries to use pkg-config to locate it. All the config options, such as PKG_CONFIG_ALLOW_CROSS, PKG_CONFIG_ALL_STATIC etc., of the crate pkg-config apply.
• Then, for MSVC ABI builds the build script will attempt use the library from a vcpkg installation if there is one available. You may need to set VCPKG_ROOT (or run vcpkg integrate install), set VCPKGRS_DYNAMIC=1, and run vcpkg install libpq:x64-windows. See the documentation for the vcpkg crate for more.
• If it still can't locate the library, it will invoke the Postgres command pg_config --libdir

[weiznich]

This was implemented by #45