Get job-specific configuration from matrix in build workflow

The "build" workflow builds the application for a range of target hosts. This is done by using a job matrix. A separate
parallel job runs for each target. The target-specific configuration data is defined in the job matrix array.

This configuration data includes the information related to the code signing certificates. Inexplicably, during the work
to add support for signing the Windows builds with an "eToken" hardware authentication device, this data was not used
for the Windows code signing configuration. Instead the certificate data was redundantly hardcoded into the workflow
code.

The Windows code signing certificate configuration is hereby changed to use the established flexible job configuration
data system. This makes the workflow easier to understand and maintain.

Author: per1234

Diff for: .github/workflows/build.yml

@@ -288,8 +288,8 @@ jobs:
       # We are hardcoding the path for signtool because is not present on the windows PATH env var by default.
       # Keep in mind that this path could change when upgrading to a new runner version
       SIGNTOOL_PATH: "C:/Program Files (x86)/Windows Kits/10/bin/10.0.19041.0/x86/signtool.exe"
-      WIN_CERT_PASSWORD: ${{ secrets.INSTALLER_CERT_WINDOWS_PASSWORD }}
-      WIN_CERT_CONTAINER_NAME: ${{ secrets.INSTALLER_CERT_WINDOWS_CONTAINER }}
+      WIN_CERT_PASSWORD: ${{ secrets[matrix.config.certificate-password-secret] }}
+      WIN_CERT_CONTAINER_NAME: ${{ secrets[matrix.config.certificate-container] }}
       WIN_SIGNING_ENABLED: ${{ !github.event.pull_request.head.repo.fork }}
 
     strategy: