docs/HTTP3.md: update the build instruction using gnutls

In ngtcp2 the `with-gnutls` option is disabled by default, which will
cause `curl` unable to be `make` because of lacking the libraries
needed.

Closes #6857

diff --git a/docs/HTTP3.md b/docs/HTTP3.md
index d738091745412d25e4a48278a949dab79dbc874f..0acbc18ed2f94d7d70cbdd4040de1bb147dd6bf7 100644 (file)
--- a/docs/HTTP3.md
+++ b/docs/HTTP3.md
@@ -95,7 +95,7 @@ Build ngtcp2
      % git clone https://github.com/ngtcp2/ngtcp2
      % cd ngtcp2
      % autoreconf -i
-     % ./configure PKG_CONFIG_PATH=<somewhere1>/lib/pkgconfig:<somewhere2>/lib/pkgconfig LDFLAGS="-Wl,-rpath,<somewhere1>/lib" --prefix=<somewhere3> --enable-lib-only
+     % ./configure PKG_CONFIG_PATH=<somewhere1>/lib/pkgconfig:<somewhere2>/lib/pkgconfig LDFLAGS="-Wl,-rpath,<somewhere1>/lib" --prefix=<somewhere3> --enable-lib-only --with-gnutls
      % make
      % make install