Boost: Add notice if legacy concatenation files are used #69962

Job	Run time
Changelogger use	25s
detect changed files	8s
Changelogger validity	36s
Copied files are in sync	7s
Project structure	1m 39s
PHP Compatibility	1m 29s
PHP lint (7.2)	39s
PHP Code Sniffer (non-excluded files only)	2m 0s
PHP lint (7.4)	38s
ESLint (non-excluded files only)	3m 25s
PHP lint (8.0)	46s
PHP lint (8.1)	44s
ESLint (changes to excluded files only)	0s
PHP lint (8.2)	46s
Lint GitHub Actions yaml files	0s
PHP lint (8.3)	52s
PHP lint (8.4)	40s
PHP Code Sniffer (changes to excluded files only)	0s
Lock files are up to date	0s
Check linter exclude lists	0s
Monorepo package version refs	0s
	14m 54s

Provide feedback