build: require C11
The atomics support used in libdispatch requires C11. Ensure that the
compiler supports it and that the support is enabled.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 19ea9e0..97d306d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,9 +8,13 @@
LANGUAGES C CXX)
enable_testing()
-set(CMAKE_C_VISIBILITY_PRESET hidden)
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED YES)
+
set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_C_VISIBILITY_PRESET hidden)
+
set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
set(THREADS_PREFER_PTHREAD_FLAG TRUE)
find_package(Threads REQUIRED)
