Allow setting the MySQL scripts location

Some of the MySQL tools are simple shell scripts and may be installed in custom locations.
We now have a MYSQLD_SCRIPTS_PATH variable that can be set to point to the scripts dir.

CCBUG: 409224
2 jobs for !52 with work/mysqld_scripts_path in 14 minutes and 39 seconds (queued for 52 minutes and 57 seconds)
latest detached
Status Job ID Name Coverage
failed #96884


passed #96883
linux kf5-qt5 qt5.15


Name Stage Failure
build_clazy_clang_tidy Build
Cloning into '/build/ci-tooling/kde-build-metadata'...
error: RPC failed; HTTP 500 curl 22 The requested URL returned error: 500
fatal: error reading section header 'shallow-info'
Uploading artifacts for failed job
Uploading artifacts...
WARNING: build/clang-tidy-report.xml: no matching files
ERROR: No files to upload
Cleaning up file based variables
ERROR: Job failed: exit code 1