doc: Update dependency installation for Debian/Ubuntu and CI

According to the description for pkg-config, "pkgconf is a
replacement for pkg-config, providing additional functionality
while also maintaining compatibility. This package only provides
a dependency link to the pkgconf package to help with package
upgrades. It can be safely removed."

Thus several scripts and markdown files are updated.

doc/build-unix.md

@@ -44,7 +44,7 @@ Finally, clang (often less resource hungry) can be used instead of gcc, which is
 
 Build requirements:
 
-    sudo apt-get install build-essential cmake pkg-config python3
+    sudo apt-get install build-essential cmake pkgconf python3
 
 Now, you can either build from self-compiled [depends](#dependencies) or install the required dependencies: