[cmake] always define _GNU_SOURCE

first.h only defines _GNU_SOURCE if no config.h is present.

src/CMakeLists.txt

@@ -687,7 +687,6 @@ if(CMAKE_COMPILER_IS_GNUCC)
 	set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_WITHDEBINFO} -O2")
 	set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${WARN_LDFLAGS}")
 	set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${WARN_LDFLAGS}")
-	add_definitions(-D_GNU_SOURCE)
 endif()
 
 if((NOT APPLE) OR CMAKE_COMPILER_IS_GNUCC)

src/config.h.cmake

@@ -8,6 +8,10 @@
 #define PACKAGE_VERSION "${PACKAGE_VERSION}"
 #define LIBRARY_DIR "${LIGHTTPD_LIBRARY_DIR}"
 
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
+
 /* System */
 #cmakedefine  HAVE_SYS_DEVPOLL_H
 #cmakedefine  HAVE_SYS_EPOLL_H