Install pkg-config for MacOS release CI (#3908)

The github actions/azure devops MacOS image update `20230214.1` removed an implicit installation of pkg-config. This works around the issue but installing pkg-config from brew.

This can be removed if the CI images get an explicit install of pkg-config, i.e actions/runner-images#7125 .

---
TYPE: NO_HISTORY
DESC: NO_HISTORY

scripts/azure-linux_mac-release.yml

@@ -9,6 +9,14 @@ steps:
     printenv
   displayName: 'Print env'
 
+- bash: |
+    # This stage is needed until https://github.com/actions/runner-images/pull/7125 or similar is merged
+    # MacOS image 20230214.1 removed implicit installation of pkg-config
+    set -e pipefail
+    brew install pkg-config
+  condition: eq(variables['Agent.OS'], 'Darwin')
+  displayName: 'Install brew package for pkg-config (OSX only)'
+
 - bash: |
     set -e pipefail
     brew uninstall --ignore-dependencies libidn2 brotli rtmpdump