compilation fails with libgcrypt 1.11 (libgcrypt-config is deprecated and got removed)

[Narrat]

Expected behavior

Compilation should succeed with libgcrypt 1.11.x

Actual behavior

Compilation fails with libgcrypt 1.11.x

Steps to resolve

Exactly like the issue reported for openvas-scanner, gsad also uses libgcrypt-config for obtaining information about libgcrypt.
libgcrypt-config was a long time deprecated and got removed with the latest release to 1.11.x
Similar report: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1070905
The respective change: https://dev.gnupg.org/T5034 ; https://dev.gnupg.org/T7165

It is advised to either use pkg-config or gpgrt-config (the replacement for the various *-config) when bootstrapping.
Therefore a change like it was done with greenbone/openvas-scanner#1694 is sufficient.