chore(windows): bump Toxcore version to the latest (0.2.8)

windows/cross-compile/build.sh

@@ -884,8 +884,8 @@ fi
 # Toxcore
 
 TOXCORE_PREFIX_DIR="$DEP_DIR/libtoxcore"
-TOXCORE_VERSION=0.2.7
-TOXCORE_HASH=bef6dbb06d921af58c6a2d7629e6f8eeafa1e541d379e4ff2ccb4ff5d3499cd1
+TOXCORE_VERSION=0.2.8
+TOXCORE_HASH="47fe125d8558775a03a3ded58e9faa07a01cfecd65257e24b544b4b5698d9362"
 TOXCORE_FILENAME="c-toxcore-$TOXCORE_VERSION.tar.gz"
 if [ ! -f "$TOXCORE_PREFIX_DIR/done" ]
 then
@@ -916,7 +916,6 @@ then
 
   cmake -DCMAKE_INSTALL_PREFIX=$TOXCORE_PREFIX_DIR \
         -DBOOTSTRAP_DAEMON=OFF \
-        -DWARNINGS=OFF \
         -DCMAKE_BUILD_TYPE=Release \
         -DENABLE_STATIC=ON \
         -DENABLE_SHARED=OFF \