Update before_script.msvc.sh

CI/before_script.msvc.sh

@@ -421,7 +421,7 @@ fi
 			rm -rf Boost
 			REAL_TEMP_PATH=`cd ${TMP} && pwd -W`
 			"${DEPS}/boost-1.67.0-msvc${MSVC_YEAR}-win${BITS}.exe" //DIR="${REAL_TEMP_PATH}\boost" //VERYSILENT //NORESTART //SUPPRESSMSGBOXES //LOG="boost_install.log"			
-			mv "${REAL_TEMP_PATH}\boost" ${BOOST_SDK}
+			mv "${REAL_TEMP_PATH}/boost" ${BOOST_SDK}
 		fi
 
 		add_cmake_opts -DBOOST_ROOT="$BOOST_SDK" \