Use Invoke-WebRequest instead of choco to install z3 on Windows

Because the `choco` installation of `z3` seems to be broken/outdated.

Using `Invoke-WebRequest` instead of `choco` allows us to pin the
version installed and to get a version which includes the `z3.exe`, not
just `z3.dll`. Using `nuget` was also considered, so that we were still
using a package manager. But the up to date `nuget` package was missing
the `.exe` file.

`wget` is supposed to be aliased to `Invoke-WebRequest` in powershell.
However `Invoke-WebRequest` is used rather than `wget` as `wget` does
not seem to work for windows github actions jobs.

Author: thomasspriggs

.github/workflows/pull-request-checks.yaml

@@ -248,9 +248,12 @@ jobs:
           submodules: recursive
       - name: Fetch dependencies
         run: |
-          choco install winflexbison3 z3
+          choco install winflexbison3
           nuget install clcache -OutputDirectory "c:\tools" -ExcludeVersion -Version 4.1.0
           echo "c:\tools\clcache\clcache-4.1.0" >> $env:GITHUB_PATH
+          Invoke-WebRequest -Uri https://github.com/Z3Prover/z3/releases/download/z3-4.8.10/z3-4.8.10-x64-win.zip -OutFile .\z3.zip
+          Expand-Archive -LiteralPath '.\z3.Zip' -DestinationPath C:\tools
+          echo "c:\tools\z3-4.8.10-x64-win\bin;" >> $env:GITHUB_PATH
       - name: Setup Visual Studio environment
         uses: microsoft/setup-msbuild@v1.0.2
       - name: Prepare ccache
@@ -287,11 +290,14 @@ jobs:
           submodules: recursive
       - name: Fetch dependencies
         run: |
-          choco install winflexbison3 strawberryperl z3
+          choco install winflexbison3 strawberryperl
           nuget install clcache -OutputDirectory "c:\tools" -ExcludeVersion -Version 4.1.0
           echo "c:\tools\clcache\clcache-4.1.0" >> $env:GITHUB_PATH
           echo "c:\ProgramData\chocolatey\bin" >> $env:GITHUB_PATH
           echo "c:\Strawberry\" >> $env:GITHUB_PATH
+          Invoke-WebRequest -Uri https://github.com/Z3Prover/z3/releases/download/z3-4.8.10/z3-4.8.10-x64-win.zip -OutFile .\z3.zip
+          Expand-Archive -LiteralPath '.\z3.Zip' -DestinationPath C:\tools
+          echo "c:\tools\z3-4.8.10-x64-win\bin;" >> $env:GITHUB_PATH
       - name: Setup MSBuild
         uses: microsoft/setup-msbuild@v1.0.2
       - name: Initialise Developer Command Line