Add warnings in debug build, and -Werror with ASan

- warnings in debug build allows the to be caught earlier
- -Werror with ASan make tests/scripts/all.sh a bit shorter
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index b8a125c..2e4d9d4 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -32,7 +32,7 @@
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-unused-function -Wno-unused-value")
 set(CMAKE_C_FLAGS_CHECK "${CMAKE_C_FLAGS_CHECK} -Wno-unused-function -Wno-unused-value")
 if(CMAKE_COMPILER_IS_CLANG)
-    set(CMAKE_C_FLAGS_CHECK "${CMAKE_C_FLAGS_CHECK} -Wno-unreachable-code")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-unreachable-code")
 endif(CMAKE_COMPILER_IS_CLANG)
 
 add_test_suite(aes aes.ecb)