Document that OUT_DIR is set during compilation for packages with build scripts

diff --git a/src/doc/environment-variables.md b/src/doc/environment-variables.md
index 01ed64b22bce6f7cbfb0cd5be066c15e7dd79897..7cb67b6c19e9c451f75d2d1003221e953c5876c2 100644 (file)
--- a/src/doc/environment-variables.md
+++ b/src/doc/environment-variables.md
@@ -49,6 +49,8 @@ let version = env!("CARGO_PKG_VERSION");
 * `CARGO_PKG_NAME` - The name of your package.
 * `CARGO_PKG_DESCRIPTION` - The description of your package.
 * `CARGO_PKG_HOMEPAGE` - The home page of your package.
+* `OUT_DIR` - If the package has a build script, this is set to the folder where the build
+              script should place its output.  See below for more information.
 
 # Environment variables Cargo sets for build scripts