Update portable_build_tools to v2.8.1 (#5901)

packages/p/portable_build_tools/xmake.lua

@@ -5,6 +5,7 @@ package("portable_build_tools")
 
     add_urls("https://github.com/Data-Oriented-House/PortableBuildTools/releases/download/$(version)/PortableBuildTools.exe")
 
+    add_versions("v2.8.1", "5663660d0e61cdc7e57a74a8dfc30337895a1cd56d345fe62556bcdb6b896d84")
     add_versions("v2.8", "d3a419be62856ab8896004f91af58f5928ce7c536954398d02a8b99202c4808f")
 
     on_install("@windows", "@msys", function (package)