Disable warning -Wno-unused-value for gcc 10 (CI)

.github/workflows/ci.yml

@@ -249,6 +249,7 @@ jobs:
               -fsanitize=address,undefined,alignment,bool,shift,shift-exponent,shift-base,integer-divide-by-zero,unreachable,null,return,bounds,bounds-strict,object-size,float-divide-by-zero,float-cast-overflow,enum,pointer-overflow,builtin
               -fno-sanitize-recover=all
               -fno-sanitize=vptr
+              -Wno-unused-value
             cmake_options: '-DOLD_LIBSTDCPP=TRUE'
 
           # - name: 'gcc 10'