packaging: add newly-required python3 build dependency for client-qt

https://review.jami.net/c/jami-client-qt/+/19283 recently marked
Python 3 as a required build depdendency for building client-qt,
as it's needeed for generating 'resources.qrc' in build time.

Change-Id: Ib7eb3822ec5af5e4223d8a05b52d7cb5bb22e8d5

packaging/rules/debian/control

@@ -10,6 +10,7 @@ Build-Depends: debhelper (>= 9),
                autotools-dev,
 # qt client
                libqt-jami,
+               python3,
 # both qt client and gnome client
                libnm-dev,
                libnotify-dev,

packaging/rules/rpm/jami-qt.spec

@@ -23,6 +23,9 @@ BuildRequires: cmake
 BuildRequires: gcc-c++
 BuildRequires: make
 
+# For generating resources.qrc in build time.
+BuildRequires: python3
+
 # Build and runtime dependencies.
 BuildRequires: qrencode-devel
 

packaging/rules/snap/jami/snapcraft.yaml

@@ -329,6 +329,7 @@ parts:
     - libvdpau-dev
     - libyaml-cpp-dev
     - nasm # seems to be needed for building libvpx on an 18.04 base
+    - python3
     - qt515base
     - qt515declarative
     - qt515graphicaleffects