Bump LLVM version to 16.0.6 and UPX to 4.0.2

Context: dotnet/maui#14531
Context: https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-erref/596a1078-e883-4972-9bbc-49e60bebca55
Context: upx/upx#594

`llc.exe` (and `lld.exe` as well, potentially) appear to sometimes die
because of access violation (NTSTATUS code 0xC0000005) on Windows 10 and
Windows 11.  The current suspicion is that it's either the UPX stub
produced by UPX 3.96 we've been using so far that crashes, or that
there's something wrong with LLVM 15.x.

Since we want to update LLVM to v16 anyway, this commit bumps it to
16.0.6 at the same time updating UPX to version 4.0.2 which appears to
have fixes for a similar crash.

Author: grendello

download-upx.ps1

@@ -1,7 +1,7 @@
-$UpxVer="3.96"
+$UpxVer="4.0.2"
 
 $progresspreference = 'silentlyContinue'
-Invoke-WebRequest https://github.com/upx/upx/releases/download/v$UpxVer/upx-3.96-win64.zip -OutFile upx.zip
+Invoke-WebRequest https://github.com/upx/upx/releases/download/v$UpxVer/upx-$UpxVer-win64.zip -OutFile upx.zip
 $progressPreference = 'Continue'
 
 $7zipPath="C:\Program Files\7-Zip\7z.exe"