This diff adds a new syntax for describing a build, which only requires
an entry in the configuration file instead of a script. Here are the
rules:
- If a script is defined, only the script is run.
- Otherwise, the configuration can define a list of targets, each entry
being a list of the targets to run in parallel. They are run in order.
Example: the following configuration:
```
targets": [
["all", "install"],
["check", "check-functional"]
]
```
will lead to the following calls:
```
ninja all install
ninja check check-functional
```
- An optional `configuration` list takes arguments to be passed to
cmake.
- A few common options are also implemented as shortcuts, and match the
options from the `build_cmake.sh` script.
The features allow for converting about the half of the tests. More will
be converted later as features are added.
Depends on D7314.