Add --workspace-concurrency=1 workaround for build tools to fix test breaks (#25326)

## Description

Add --workspace-concurrency=1 workaround for build tools to fix test
breaks.

This mitigates a bug (
[AB#47469](https://dev.azure.com/fluidframework/235294da-091d-4c29-84fc-cdfc3d90890b/_workitems/edit/47469)
) where running the tests for built-tools usually fails due to some
concurrency issue which seems to be related to its use of git.

Author: CraigMacomber

build-tools/package.json

@@ -50,7 +50,8 @@
 		"test:bail": "npm run test:mocha:bail",
 		"test:copyresults": "copyfiles --exclude \"**/node_modules/**\" \"**/nyc/**\" nyc",
 		"test:coverage": "c8 npm run test:mocha",
-		"test:mocha": "pnpm run -r --no-sort --stream --no-bail test:mocha --color",
+		"test:mocha": "pnpm run -r --no-sort --workspace-concurrency=1 --stream --no-bail test:mocha --color",
+		"test:mocha-comment": "echo TODO:AB#47469: --workspace-concurrency=1 is a workaround for bug",
 		"test:mocha:bail": "pnpm run -r --no-sort --stream test:mocha",
 		"tsc": "fluid-build --task tsc",
 		"tsc:fast": "fluid-build --root . --task tsc --worker",