From: Julian Ospald <hasufell@gentoo.org>
Date: Sat Oct 25 17:12:43 UTC 2014
Subject: respect system cflags

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,7 +4,7 @@
 string(REGEX MATCH "Clang" CMAKE_COMPILER_IS_CLANG "${CMAKE_C_COMPILER_ID}")
 
 if(CMAKE_COMPILER_IS_GNUCC)
-  set(CMAKE_C_FLAGS "-Wall -Wextra -W -Wdeclaration-after-statement -Wlogical-op -Wwrite-strings")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -W -Wdeclaration-after-statement -Wlogical-op -Wwrite-strings")
   set(CMAKE_C_FLAGS_RELEASE "-O2")
   set(CMAKE_C_FLAGS_DEBUG "-g3 -O0")
   set(CMAKE_C_FLAGS_COVERAGE "-g3 -O0 --coverage")