Support multiple GitHub SSH deploy keys (#568)

* add sshPublicKeysDirectoryPath and GIT_CONFIG_EXTENSIONS parameters that adds git configs and mounts .ssh/config and public keys to the container, in order to allow multiple sh deploy key trick by webplatform@ssh-agent

* remove sshPublicKeysDirectoryPath and GIT_CONFIG_EXTENSIONS from windows runner for now

dist/platforms/ubuntu/entrypoint.sh

@@ -10,6 +10,7 @@ mkdir -p "$ACTIVATE_LICENSE_PATH"
 #
 # Run steps
 #
+source /steps/set_extra_git_configs.sh
 source /steps/set_gitcredential.sh
 source /steps/activate.sh
 source /steps/build.sh

dist/platforms/ubuntu/steps/set_extra_git_configs.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+if [ -z "${GIT_CONFIG_EXTENSIONS}" ]
+then
+  echo "GIT_CONFIG_EXTENSIONS unset skipping"
+else
+  echo "GIT_CONFIG_EXTENSIONS is set configuring extra git configs"
+
+  IFS=$'\n'
+  for config in $(echo "${GIT_CONFIG_EXTENSIONS}" | sed 's/\(.*\)=\(.*\)/"\1" "\2"/g'); do
+    if [[ $config =~ \"([^\"]+)\"\ \"([^\"]+)\" ]]; then
+      key="${BASH_REMATCH[1]}"
+      value="${BASH_REMATCH[2]}"
+    else
+      echo "Error parsing config: $config"
+      exit 1
+    fi
+    echo "Adding extra git config: \"$key\" = \"$value\""
+    git config --global --add "$key" "$value"
+  done
+  unset IFS
+
+fi
+
+echo "---------- git config --list -------------"
+git config --list
+
+echo "---------- git config --list --show-origin -------------"
+git config --list --show-origin