patch out a cfg(bootstrap) we can't work around currently

Author: RalfJung

rust-src.diff

@@ -0,0 +1,21 @@
+diff --git a/library/core/src/iter/sources/generator.rs b/library/core/src/iter/sources/generator.rs
+index c94232e09eb..155fa9368ad 100644
+--- a/library/core/src/iter/sources/generator.rs
++++ b/library/core/src/iter/sources/generator.rs
+@@ -9,8 +9,6 @@
+ ///
+ /// ```
+ /// #![feature(iter_macro, coroutines)]
+-/// # #[cfg(not(bootstrap))]
+-/// # {
+ ///
+ /// let it = std::iter::iter!{|| {
+ ///     yield 1;
+@@ -19,7 +17,6 @@
+ /// } }();
+ /// let v: Vec<_> = it.collect();
+ /// assert_eq!(v, [1, 2, 3]);
+-/// # }
+ /// ```
+ #[unstable(feature = "iter_macro", issue = "none", reason = "generators are unstable")]
+ #[allow_internal_unstable(coroutines, iter_from_coroutine)]