utils: refactor Fetch-Dependencies for future changes

Future work to enable Android SDKs requires fetching additional
dependencies (e.g. Android NDK). Refactor the fetch dependencies method
to allow us to share the download logic rather than replicating it for
each piece. This will also allow us to fetch the Python dependency for
the ARM64 toolchain cross-compilation.

Author: compnerd

utils/build.ps1

@@ -446,41 +446,37 @@ function Fetch-Dependencies {
 
   $WebClient = New-Object Net.WebClient
 
-  $WiXVersion = "4.0.4"
-  $WiXURL = "https://www.nuget.org/api/v2/package/wix/$WiXVersion"
-  $WiXHash = "A9CA12214E61BB49430A8C6E5E48AC5AE6F27DC82573B5306955C4D35F2D34E2"
+  function DownloadAndVerify($URL, $Destination, $Hash) {
+    if (Test-Path $Destination) {
+      return
+    }
 
-  if (-not (Test-Path $BinaryCache\WiX-$WiXVersion.zip)) {
-    Write-Output "WiX not found. Downloading from nuget.org ..."
-    New-Item -ItemType Directory -ErrorAction Ignore $BinaryCache | Out-Null
+    Write-Output "$Destination not found. Downloading ..."
     if ($ToBatch) {
-      Write-Output "curl.exe -sL $WiXURL -o $BinaryCache\WiX-$WiXVersion.zip"
+      Write-Output "md `"$(Split-Path -Path $Destination -Parent)`""
+      Write-Output "curl.exe -sL $URL -o $Destination"
+      Write-Output "(certutil -HashFile $Destination SHA256) == $Hash || (exit /b)"
     } else {
-      $WebClient.DownloadFile($WiXURL, "$BinaryCache\WiX-$WiXVersion.zip")
-      $SHA256 = Get-FileHash -Path "$BinaryCache\WiX-$WiXVersion.zip" -Algorithm SHA256
-      if ($SHA256.Hash -ne $WiXHash) {
-        throw "WiX SHA256 mismatch ($($SHA256.Hash) vs $WiXHash)"
+      New-Item -ItemType Directory (Split-Path -Path $Destination -Parent) -ErrorAction Ignore | Out-Null
+      $WebClient.DownloadFile($URL, $Destination)
+      $SHA256 = Get-FileHash -Path $Destination -Algorithm SHA256
+      if ($SHA256.Hash -ne $Hash) {
+        throw "SHA256 mismatch ($($SHA256.Hash) vs $Hash)"
       }
     }
   }
 
+  $WiXVersion = "4.0.4"
+  $WiXURL = "https://www.nuget.org/api/v2/package/wix/$WiXVersion"
+  $WiXHash = "A9CA12214E61BB49430A8C6E5E48AC5AE6F27DC82573B5306955C4D35F2D34E2"
+  DownloadAndVerify $WixURL "$BinaryCache\WiX-$WiXVersion.zip" $WiXHash
+
   # TODO(compnerd) stamp/validate that we need to re-extract
   New-Item -ItemType Directory -ErrorAction Ignore $BinaryCache\WiX-$WiXVersion | Out-Null
   Write-Output "Extracting WiX ..."
   Expand-Archive -Path $BinaryCache\WiX-$WiXVersion.zip -Destination $BinaryCache\WiX-$WiXVersion -Force
 
-  if (-not (Test-Path $BinaryCache\$PinnedToolchain.exe)) {
-    Write-Output "Swift toolchain not found. Downloading from swift.org..."
-    if ($ToBatch) {
-      Write-Output "curl.exe -sL $PinnedBuild -o $BinaryCache\$PinnedToolchain.exe"
-    } else {
-      $WebClient.DownloadFile("$PinnedBuild", "$BinaryCache\$PinnedToolchain.exe")
-      $SHA256 = Get-FileHash -Path "$BinaryCache\$PinnedToolchain.exe" -Algorithm SHA256
-      if ($SHA256.Hash -ne $PinnedSHA256) {
-        throw "$PinnedToolchain SHA256 mismatch ($($SHA256.Hash) vs $PinnedSHA256)"
-      }
-    }
-  }
+  DownloadAndVerify $PinnedBuild "$BinaryCache\$PinnedToolchain.exe" $PinnedSHA256
 
   # TODO(compnerd) stamp/validate that we need to re-extract
   Write-Output "Extracting $PinnedToolchain ..."