Revert "SWPROT-8953: libs2: Relax Werror for release, to be reverted"

One would argue that libs2 warnings should not be addressed
in the consumming project, but until a better architecture is in place,
we can enable it to detect issues and help fixing them at the root.
If for any reason having this patch is a problem,
I encourage to cherry-pick the 1st Bypass change
(that would be applied in next release)

This reverts commit 436ef26.

Origin: #37
Relate-to: #28
Signed-off-by: Philippe Coval <philippe.coval@silabs.com>

applications/zpc/components/zwave/zwave_transports/s2/libs/zw-libs2/CMakeLists.txt

@@ -8,7 +8,7 @@ if("${PROJECT_NAME}" STREQUAL "")
   add_definitions(-Dx86)
 
   if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID MATCHES "Clang")
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Werror")
     # For gov/cobertura: do not use .c.o on the object files, only .o
     set(CMAKE_C_OUTPUT_EXTENSION_REPLACE 1)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fprofile-arcs -ftest-coverage")