Update README for new versioning scheme + env vars

ctru-sys/README.md

@@ -10,23 +10,16 @@ to use this library.
 
 ## Version
 
-This crate's version changes according to the version of `libctru`
-used to generate the bindings, with the following convention:
-
-  * [`libctru`](https://github.com/devkitPro/libctru) version `X.Y.Z-W`
-  * `ctru-sys` version `XY.Z.P+X.Y.Z-W`
-
-  where `P` is usually 0 but may be incremented for fixes in e.g.
-  binding generation, `libc` dependency bump, etc.
-
-It may be possible to build this crate against a different version of [`libctru`](https://github.com/devkitPro/libctru),
-but you may encounter linker errors or ABI issues. A build-time Cargo warning
-(displayed when built with `-vv`) will be issued if the build script detects
-a mismatch or is unable to check the installed [`libctru`](https://github.com/devkitPro/libctru) version.
-
-## Generating bindings
-
-Bindings of new versions of [`libctru`](https://github.com/devkitPro/libctru) can be built using the integrated [`bindgen.sh`](./bindgen.sh) script.
+Crate bindings are generated at build time, so the available APIs will depend on the
+installed version of `libctru` when the crate is built. If you want to check
+what version of `libctru` is being built, you can examine these environment
+variables with [`env!`](https://doc.rust-lang.org/std/macro.env.html):
+
+* `LIBCTRU_VERSION`: full version string (e.g. `"2.3.1-4"`)
+* `LIBCTRU_MAJOR`: major version (e.g. `"2"` for version `2.3.1-4`)
+* `LIBCTRU_MINOR`: minor version (e.g. `"3"` for version `2.3.1-4`)
+* `LIBCTRU_PATCH`: patch version (e.g. `"1"` for version `2.3.1-4`)
+* `LIBCTRU_RELEASE`: release version (e.g. `"4"` for version `2.3.1-4`)
 
 ## License