Fixed building with external FORTIFY_SOURCE

source/CMakeLists.txt

@@ -67,9 +67,15 @@ add_custom_target(
 
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -Werror -Wmissing-declarations -fdiagnostics-color=always \
 	-O2 -pipe -fno-plt -fexceptions \
-        -Wp,-D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security \
+        -Wformat -Werror=format-security \
         -fstack-clash-protection -fcf-protection")
         
+string(FIND "${CMAKE_CXX_FLAGS}" "-D_FORTIFY_SOURCE" FORTIFY_FOUND)
+
+if(FORTIFY_FOUND EQUAL -1)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wp,-D_FORTIFY_SOURCE=2")
+endif()
+
 set(SOURCE_FILES
         ubl-settings-kernel.c
         ubl-settings-kernel.h