docs/HYPER.md: updated to reflect current hyper build needs

diff --git a/docs/HYPER.md b/docs/HYPER.md
index 0ca1ce1d4faa8a6b1febf7f8fb8e10e91a7f8c2d..a0f39696bdb6fd77f508078e11a53bc414669cd3 100644 (file)
--- a/docs/HYPER.md
+++ b/docs/HYPER.md
@@ -18,11 +18,16 @@ The C API for Hyper is brand new and is still under development.
 
 ## build curl with hyper
 
-Build hyper and enable the C API:
+Since March 3 2022, hyper needs the nightly rustc to build, which you may need
+to install first with:
+
+     % rustup toolchain install nightly
+
+Then build hyper and enable its C API like this:
 
      % git clone https://github.com/hyperium/hyper
      % cd hyper
-     % RUSTFLAGS="--cfg hyper_unstable_ffi" cargo build --features client,http1,http2,ffi
+     % RUSTFLAGS="--cfg hyper_unstable_ffi" cargo +nightly rustc --features client,http1,http2,ffi -Z unstable-options --crate-type cdylib
 
 Build curl to use hyper's C API: