debugging %build-inputs

[jgart]

Hi,

How can I debug what %build-inputs is in the context of the package being built?

    (arguments
     `(#:configure-flags
       (list (string-append "--with-tcl="
                            (assoc-ref %build-inputs "tcl")
                            "/lib")    ^^^^^^^^^^^^
             (string-append "--with-tk="
                            (assoc-ref %build-inputs "tk")
                            "/lib"))))


The above snippet is from gtkwave (e.g. guix edit gtkwave).

What I would like to do is drop into a debugger in the environment where I can 
print %build-inputs.

If I can't do it that way what is the Guiler way to achieve what I'm trying to 
do?

Any advice and enlightment would be much appreciated.

all best,

jgart