Document supported-crate-types print request in rustc book

Author: jieyouxu

src/doc/rustc/src/command-line-arguments.md

@@ -292,6 +292,9 @@ The valid types of print values are:
   components alongside a Rust build that need this information, such as C compilers.
   This returns rustc's minimum supported deployment target if no `*_DEPLOYMENT_TARGET` variable
   is present in the environment, or otherwise returns the variable's parsed value.
+- `supported-crate-types` — Which crate types are supported for the given target.
+  The output is a list of newline-delimited crate types (the values correspond to the
+  crate type strings accepted by `--crate-type`).
 
 A filepath may optionally be specified for each requested information kind, in
 the format `--print KIND=PATH`, just like for `--emit`. When a path is