Enable signing Windows builds with SHA1 environment variable (GH-11279)

PCbuild/pyproject.props

@@ -187,10 +187,11 @@ public override bool Execute() {
     <SdkBinPath Condition="!Exists($(SdkBinPath))">$(registry:HKEY_LOCAL_MACHINE\Software\Microsoft\Windows Kits\Installed Roots@KitsRoot)\bin\x86</SdkBinPath>
     <SdkBinPath Condition="!Exists($(SdkBinPath))">$(registry:HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SDKs\Windows\v7.1A@InstallationFolder)\Bin\</SdkBinPath>
     <_SignCommand Condition="Exists($(SdkBinPath)) and '$(SigningCertificate)' != '' and $(SupportSigning)">"$(SdkBinPath)\signtool.exe" sign /q /a /n "$(SigningCertificate)" /fd sha256 /t http://timestamp.verisign.com/scripts/timestamp.dll /d "Python $(PythonVersion)"</_SignCommand>
+    <_SignCommand Condition="Exists($(SdkBinPath)) and '$(SigningCertificateSha1)' != '' and $(SupportSigning)">"$(SdkBinPath)\signtool.exe" sign /q /a /sha1 "$(SigningCertificateSha1)" /fd sha256 /t http://timestamp.verisign.com/scripts/timestamp.dll /d "Python $(PythonVersion)"</_SignCommand>
     <_MakeCatCommand Condition="Exists($(SdkBinPath))">"$(SdkBinPath)\makecat.exe"</_MakeCatCommand>
   </PropertyGroup>
-  
-  <Target Name="_SignBuild" AfterTargets="AfterBuild" Condition="'$(SigningCertificate)' != '' and $(SupportSigning)">
+
+  <Target Name="_SignBuild" AfterTargets="AfterBuild" Condition="'$(_SignCommand)' != '' and $(SupportSigning)">
     <Error Text="Unable to locate signtool.exe. Set /p:SignToolPath and rebuild" Condition="'$(_SignCommand)' == ''" />
     <Exec Command='$(_SignCommand) "$(TargetPath)" || $(_SignCommand) "$(TargetPath)" || $(_SignCommand) "$(TargetPath)"' ContinueOnError="false" />
   </Target>

Tools/msi/sdktools.psm1

@@ -21,6 +21,9 @@ function Sign-File {
             $description = "Python";
         }
     }
+    if (-not $certsha1) {
+        $certsha1 = $env:SigningCertificateSha1;
+    }
     if (-not $certname) {
         $certname = $env:SigningCertificate;
     }
@@ -32,7 +35,7 @@ function Sign-File {
         if ($certsha1) {
             SignTool sign /sha1 $certsha1 /fd sha256 /t http://timestamp.verisign.com/scripts/timestamp.dll /d $description $a
         } elseif ($certname) {
-            SignTool sign /n $certname /fd sha256 /t http://timestamp.verisign.com/scripts/timestamp.dll /d $description $a
+            SignTool sign /a /n $certname /fd sha256 /t http://timestamp.verisign.com/scripts/timestamp.dll /d $description $a
         } elseif ($certfile) {
             SignTool sign /f $certfile /fd sha256 /t http://timestamp.verisign.com/scripts/timestamp.dll /d $description $a
         } else {