When compiling upm for target Raspberry Pi (and probably others),

warning messages about unused result occur.
This commit enables to remove the messages uding the option
-DWUNUSED=on
which makes a cleaner log

Signed-off-by: g-vidal <gerard.vidal@ens-lyon.fr>

CMakeLists.txt

@@ -15,6 +15,7 @@ option (RPM "Generate RPM using CPack" OFF)
 option (NPM "Generate NPM/GYP tarballs" OFF)
 option (BUILDTESTS "Generate check-ups for upm" OFF)
 option (WERROR "Make all warnings into errors." ON)
+option (WUNUSED "Remove warnings if return value unused" OFF)
 
 # Warn if building in source root
 if ("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_BINARY_DIR}")
@@ -104,6 +105,13 @@ if (WERROR)
   message (STATUS "Warnings as errors enabled (-Werror), disable with -DWERROR=off")
 endif (WERROR)
 
+# Remove Warnings for "unused return"  ?
+if (WUNUSED)
+  list (APPEND C_CXX_WARNING_FLAGS -Wno-unused-result)
+   message (STATUS "Warnings for unused-result enabled, disable with -DWUNUSED=on")
+endif (WUNUSED)
+
+
 # Set C compiler warning flags at top-level scope and emit a warning about
 # unsupported flags
 upm_add_compile_flags(C ${C_CXX_WARNING_FLAGS}