With the Makefile generator one can use `cd $subdir; make install` to build and
install targets associated with a given subdirectory. This is not possible to
do with the Ninja generator since there is only one `build.ninja` file at the
top of the build tree. However, we can approximate it by allowing one to run
`ninja $subdir/install` at the top of the tree to build the targets in the
corresponding subdirectory and install them.
This also makes sense for `test`, `package`, and other GLOBAL_TARGET targets.
It was already done for `all` by commit v3.6.0-rc1~240^2~2 (Ninja: Add
`$subdir/all` targets, 2016-03-11).
Add a `CMAKE_NINJA_OUTPUT_PATH_PREFIX` variable. When it is set, CMake
generates a `build.ninja` file suitable for embedding into another ninja
project potentially generated by an alien generator.
Add policy CMP0058 to avoid generating 'phony' ninja rules for unknown
custom command dependencies. This requires projects to specify their
custom command byproducts explicitly. With this requirement we no
longer have to assume that unknown custom command dependencies are
generated and can instead simply assume they are source files expected
to exist when the build starts. This is particularly important in
in-source builds. It is also helpful for out-of-source builds to allow
Ninja to diagnose missing files before running custom command rules that
depend on them.
Brad King
Nicolas Despres