README for prost_reflect_build::Builder is incorrect with recent changes, as either 'descriptor_pool' or 'file_descriptor_set_bytes' must be set

[jbott]

As of 0.11, there is a requirement that either 'descriptor_pool' or 'file_descriptor_set_bytes' must be set, but the readme example does not show that.

The current code snippet is:

prost_reflect_build::Builder::new()
    .compile_protos(&["src/package.proto"], &["src"])
    .unwrap();

Since the prost-reflect-tests crate contains a fully functional example – it might make sense to point people to that in the readme
build.rs:

prost-reflect/prost-reflect-tests/build.rs

Lines 36 to 51 in 8fd210d

	prost_reflect_build::Builder::new()
	.file_descriptor_set_bytes("crate::DESCRIPTOR_POOL_BYTES")
	.compile_protos_with_config(
	config,
	&[
	"src/test.proto",
	"src/test2.proto",
	"src/desc.proto",
	"src/desc2.proto",
	"src/desc_no_package.proto",
	"src/imports.proto",
	"src/ext.proto",
	"src/options.proto",
	],
	&["src/"],
	)?;

crate lib.rs:

prost-reflect/prost-reflect-tests/src/lib.rs

Lines 25 to 26 in 8fd210d

	const DESCRIPTOR_POOL_BYTES: &[u8] =
	include_bytes!(concat!(env!("OUT_DIR"), "/file_descriptor_set.bin"));