[CMake] Scope of custom targets and commands

[Giampiero Salvi]

Hi,
As far as I understand, the scope of rules created by add_custom_target 
and add_custom_command is current directory and subdirectories, whereas 
the scope of targets created by add_library and add_executable are 
global. Is this true? Is there a way to make a custom target/command 
rule global?

What is odd is that I can run "make mycustomtarget" in a parent 
directory and it works, but if I define a dependency to mycustomtarget 
in a parent directory I get: No rule to make target `mycustomtarget'.

Any help appreciated.
Giampiero