utils: adjust the -Clean option to clean before execution

This hoists the cleaning to prior to building the toolchain. This is
particularly important as changes in the module format may cause the
compiler to crash. Due to the use of Swift in the Swift compiler, we
load modules early and a previous run may have left over modules from
the last run, which would result in the module attempting to be loaded.
This cleans out the extra modules before the toolchain build avoiding
that.

utils/build.ps1

@@ -2790,6 +2790,19 @@ try {
 
 Fetch-Dependencies
 
+if ($Clean) {
+  10..[HostComponent].getEnumValues()[-1] | ForEach-Object { Remove-Item -Force -Recurse "$BinaryCache\$_" -ErrorAction Ignore }
+  # In case of a previous test run, clear out the swiftmodules as they are not a stable format.
+  Remove-Item -Force -Recurse -Path "$($HostARch.ToolchainInstallRoot)\usr\lib\swift\windows\*.swiftmodule" -ErrorAction Ignore
+  foreach ($Arch in $WindowsSDKArchs) {
+    0..[TargetComponent].getEnumValues()[-1] | ForEach-Object { Remove-Item -Force -Recurse "$BinaryCache\$($Arch.BuildID + $_)" -ErrorAction Ignore }
+  }
+  foreach ($Arch in $AndroidSDKArchs) {
+    0..[TargetComponent].getEnumValues()[-1] | ForEach-Object { Remove-Item -Force -Recurse "$BinaryCache\$($Arch.BuildID + $_)" -ErrorAction Ignore }
+  }
+}
+
+
 if (-not $SkipBuild) {
   if ($EnableCaching -And (-Not (Test-SCCacheAtLeast -Major 0 -Minor 7 -Patch 4))) {
     throw "Minimum required sccache version is 0.7.4"
@@ -2810,18 +2823,6 @@ if (-not $SkipBuild) {
   Invoke-BuildStep Build-Compilers $HostArch
 }
 
-if ($Clean) {
-  10..[HostComponent].getEnumValues()[-1] | ForEach-Object { Remove-Item -Force -Recurse "$BinaryCache\$_" -ErrorAction Ignore }
-  # In case of a previous test run, clear out the swiftmodules as they are not a stable format.
-  Remove-Item -Force -Recurse "$($HostARch.ToolchainInstallRoot)\usr\lib\swift\windows" -ErrorAction Ignore
-  foreach ($Arch in $WindowsSDKArchs) {
-    0..[TargetComponent].getEnumValues()[-1] | ForEach-Object { Remove-Item -Force -Recurse "$BinaryCache\$($Arch.BuildID + $_)" -ErrorAction Ignore }
-  }
-  foreach ($Arch in $AndroidSDKArchs) {
-    0..[TargetComponent].getEnumValues()[-1] | ForEach-Object { Remove-Item -Force -Recurse "$BinaryCache\$($Arch.BuildID + $_)" -ErrorAction Ignore }
-  }
-}
-
 if (-not $SkipBuild) {
   foreach ($Arch in $WindowsSDKArchs) {
     Invoke-BuildStep Build-ZLib Windows $Arch