don't backup older deps after upgrades

Author: weltling

appveyor/build_task.bat

@@ -19,7 +19,7 @@ set STABILITY=staging
 set DEPS_DIR=%PHP_BUILD_CACHE_BASE_DIR%\deps-%BRANCH%-%PHP_SDK_VC%-%PHP_SDK_ARCH%
 rem SDK is cached, deps info is cached as well
 echo Updating dependencies in %DEPS_DIR%
-call phpsdk_deps --update --branch %BRANCH% --stability %STABILITY% --deps %DEPS_DIR%
+call phpsdk_deps --update --no-backup --branch %BRANCH% --stability %STABILITY% --deps %DEPS_DIR%
 if %errorlevel% neq 0 exit /b 3
 
 call buildconf.bat --force