lib: nghttp2: CMakeLists.txt: do not require a CXX compiler

Upstream:
nghttp2/nghttp2@d9d2661

Signed-off-by: Thomas Devoogdt <[email protected]>

Author: ThomasDevoogdt

lib/nghttp2/CMakeLists.txt

@@ -24,7 +24,7 @@
 
 cmake_minimum_required(VERSION 3.0)
 # XXX using 1.8.90 instead of 1.9.0-DEV
-project(nghttp2 VERSION 1.58.90)
+project(nghttp2 VERSION 1.58.90 LANGUAGES C)
 
 # See versioning rule:
 #  https://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html