Running a command always but only once (even if included Makefiles are remade)

[Christoph Groth]

Hello,

in the Makefile of my project I would like to always run (before
everything else) a command which updates the submodules of the project.

I do this by having the line

$(shell to-be-run)

somewhere in the Makefile.

However, when the automatically generated dependencies are re-generated,
which happens every time some source file has been changed, the Makefile
is re-initialized.  As a consequence, `to-be-run' is executed a second
time.

I wonder how to tell GNU make to execute a command always, but only
once, even if some of the included Makefiles are re-generated.

thanks,
Christoph