I am new to bevy, so I just cloned the repository and did a cargo build. That gave me the error:

/home/einfochips/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/wayland-sys-0.31.7/build.rs:10:47:
  called `Result::unwrap()` on an `Err` value: Failed to run command `PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 pkg-config --libs --cflags wayland-client`, because: Not a directory (os error 20)

then I discovered that my system runs on x11, but when i ran the example:

cargo run --features x11 --example hello_world

I still got the error.
This PR is trying to fix this.

Objective

Since engine runs on wayland by default, the defaults need to be disabled for running on x11.

Solution

The first example of cargo run in example/README.md needs to specify how to do this. Hence a new example is added.

Testing

I did run the cargo my self and the newly added example works on my system, the command being:

cargo run --no-default-features --features x11 --example hello_world