[android] install Chocolatey if not installed

Installs the Chocolatey package manager if it is not already installed
on the system. This is currently needed for the Azure runners but not
for GitHub runners, where Chocolatey is pre-installed.

.github/workflows/swift-toolchain.yml

@@ -306,7 +306,12 @@ jobs:
           arch: amd64
 
       - name: Install Flex and Bison Tools
-        run: choco install winflexbison3
+        run: |
+          if (-not $env:ChocolateyInstall -or -not (Test-Path "$env:ChocolateyInstall")) {
+            Invoke-Expression ((New-Object net.webclient).DownloadString("https://community.chocolatey.org/install.ps1"))
+          }
+          choco feature enable -n allowGlobalConfirmation
+          choco install winflexbison3
 
       - name: Configure RegsGen2
         run: |
@@ -387,7 +392,12 @@ jobs:
           arch: ${{ matrix.arch }}
 
       - name: Install Flex and Bison Tools
-        run: choco install winflexbison3
+        run: |
+          if (-not $env:ChocolateyInstall -or -not (Test-Path "$env:ChocolateyInstall")) {
+            Invoke-Expression ((New-Object net.webclient).DownloadString("https://community.chocolatey.org/install.ps1"))
+          }
+          choco feature enable -n allowGlobalConfirmation
+          choco install winflexbison3
 
       - uses: actions/download-artifact@v4
         with: