Update pyrcc5 note with new information

New information about the other system package which resolves the dependency
added.
This was brought up in #766.

README.md

@@ -45,12 +45,14 @@ For macos instructions (qt version) see the [macOS Instructions](macos.md).
 ### System Setup
 When running in a linux based environment the following system packages or equivalents are needed to build:
 * python3-pyqt5
+* pyqt5-dev-tools (on some systems, see note)
 * python3-wheel (for hsaudiotag3k)
 * python3-venv (only if using a virtual environment)
 * python3-dev
 * build-essential
 
-Note: On some linux systems pyrcc5 is not put on the path when installing python3-pyqt5, this will cause some issues with the resource files (and icons). It can be checked by running `which pyrcc5`. If there is no result, before building install pyqt5 just into the virtual environment via pip.  (It has not been added to the requirement files at this time on linux due to issues caused in the CI builds if this is done.)
+
+Note: On some linux systems pyrcc5 is not put on the path when installing python3-pyqt5, this will cause some issues with the resource files (and icons). These systems should have a respective pyqt5-dev-tools package, which should also be installed. The presence of pyrcc5 can be checked with `which pyrcc5`.  Debian based systems need the extra package, and Arch does not.
 
 To create packages the following are also needed:
 * python3-setuptools