The current setup is configuring the "affected projects" as well
as their dependencies, and run `ninja all` followed by
`ninja check-all`.
This is quite a pessimization for leaf project which don't need to
build and run the tests for their dependencies.
For example a patch affecting only MLIR shouldn't need to build
and run LLVM and clang tests.
This patch changes this by running checks only for the affected
project. For example a patch touching `mlir` is affecting `mlir`
and `flang`. However `flang` depends on `clang`. So the list of
projects to configure is `mlir;flang;clang;llvm;`, but we want
to test only mlir and flang ; we'll run only `ninja check-mlir
check-flang`.
In practice in this example running `ninja all` builds 5658 targets
and `ninja check-all` after that adds 716 more targets. On the other
hands `ninja check-flang check-mlir` results in 3997 targets total.
Concretely the contract with premerge_checks.py is changed so that
the expected argument for the --projects flag is only the list of
affected project, dependencies are automatically added.
6e624c30f9