Where can I find the KF5 header?

Hi, there.
I’ve started compiling LibreOffice 6. Due to lack of source on my machine, I tried with a VM on a remote server. The VM is on Ubuntu 18.04. After running the autogen.sh command, I get this error:

    configure: error: KF5 headers not found.  Please specify the root of your KF5 installation by exporting KF5DIR before running "configure".
Error running configure at ./autogen.sh line 302

I can’t find anything about this mistake in my research. Could someone help me, please?
Thank you.

Your question is off-topic here, because this site is for questions and answers about LibreOffice usage. Development issues are to be discussed on IRC and mailing lists.

Okay. Thank you.