Update the readme [ci skip]

Author: IvanUkhov

README.md

@@ -6,15 +6,18 @@ The usage of the package is explained [here][usage].
 
 The following Cargo features are supported:
 
+* `cache` to build in `.cargo` instead of `target` (see below),
 * `cblas` to build CBLAS (enabled by default),
 * `lapacke` to build LAPACKE (enabled by default),
-* `static` to link to OpenBLAS statically,
-* `system` to skip building the bundled OpenBLAS, and
-* `shared-build-cache` to place most of the OpenBLAS build products in
-  `~/.cargo` instead of the `target` directory. (This allows them to be reused
-  between crates which have different `target` directories, in order to avoid
-  rebuilding OpenBLAS unnecessarily. However, it prevents `cargo clean` from
-  removing the OpenBLAS build products.)
+* `static` to link to OpenBLAS statically, and
+* `system` to skip building the bundled OpenBLAS.
+
+## Caching
+
+The `cache` feature allows the OpenBLAS build products to be reused between
+crates that have different `target` directories. This is to avoid rebuilding
+OpenBLAS unnecessarily. However, it is worth noting that this prevents `cargo
+clean` from removing the OpenBLAS build products.
 
 ## Cross Compilation