Integration test tool for phper.

The php-config is needed. You can set environment PHP_CONFIG to specify the path.

1. Because the phper-test depends on the cdylib to do integration test, but now cargo test don't build cdylib in [lib], so you must call cargo build before cargo test.

   Maybe, when the feature artifact-dependencies becomes stable, or the issue be solved, you don't have to call cargo build in advance, but I think it will be a long long stage.

2. Or, define an [[example]] section, re-export all the symbols of your crate, and set lto = true. It's strange, but this is the only method to just run cargo test without running cargo build in advance. Please refer to tests/integration/Cargo.toml.

MulanPSL-2.0.