Added explicit Python build tools to snap requirements (#7213)

Signed-off-by: James Hebden <james@ec0.io>

changelog.d/7213.misc

@@ -0,0 +1 @@
+Add explicit Python build tooling as dependencies for the snapcraft build.

snap/snapcraft.yaml

@@ -33,6 +33,10 @@ parts:
     python-version: python3
     python-packages:
       - '.[all]'
+      - pip
+      - setuptools
+      - setuptools-scm
+      - wheel
     build-packages:
       - libffi-dev
       - libturbojpeg0-dev