qa: Enforce JSON standard for GCT configs (#1526)

* qa: Enforce JSON lint for GCT configs

* Makefile/GHA: Make output more verbose on success, clean duplicate PHONY and rid excess newlines

* Makefile: Use printf for OS cross-compatibility output

.github/workflows/configs-json-lint.yml

@@ -0,0 +1,24 @@
+name: configs-json-lint
+on: [push, pull_request]
+
+jobs:
+  lint:
+    name: configs JSON lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Check configs JSON format
+        run: |
+          files=("config_example.json" "testdata/configtest.json")
+          for file in "${files[@]}"; do
+            processed_file="${file%.*}_processed.${file##*.}"
+            jq '.exchanges |= sort_by(.name)' --indent 1 $file > $processed_file
+            if ! diff $file $processed_file; then
+              echo "jq differences found in $file! Please run 'make lint_configs'"
+              exit 1
+            else
+              rm $processed_file
+              echo "No differences found in $file 🌞"
+            fi
+          done