[CMake] Invoke a target on a separate project in a generic way?

[Hugo Heden]

Good day all,

I am looking for a way within a CMakeLists.txt make sure that:

-- at *build* time

-- cmake is invoked on a *separate* project, and then also the
"all"-target is invoked

How do I do that?

The following is a first rough sketch (that is not good enough, I believe):

ADD_CUSTOM_TARGET(
  build_separate_project
  WORKING_DIRECTORY separate_project/build
  COMMAND ${CMAKE_COMMAND} ../src
  COMMAND ${CMAKE_BUILD_TOOL} all
)

-- The above only works for a ${CMAKE_BUILD_TOOL} that happens to
accept a commandline that contains a target and nothing else (like
GNU-make does).

So is there a more *generic* way to, at build time, invoke cmake and
then the "all"-target on a separate project?

(The following is a bit of background: We have a project called "FOO"
that generates source code that eventually also needs to be compiled.
The generated source files end up in a *directory* that is known
CMake-time, but the *filenames* are not known until *build*-time. Thus
there is no way with in project "FOO" to create a target to compile
the generated source-code. (Doing FILE(GLOB...) within project FOO
will not work, because the globbing will take place at cmake-time, at
which time there are no files there). Therefore, together with the
generated source files we generate a CMakeLists.txt that defines a
*separate* project called "BAR" that contains a target to compile the
generated source code. Hence the question above -- how do I invoke the
all target in the BAR project in a way that works for all build-tools,
not only GNU-make?)

Best Regards

Hugo Heden