AppImage: Disable pip warnings about script install locations

It warns about scripts being installed in a location that is not on the
path, but that is inconsequential as they are not used.

-----

taken from Electron-Cash/Electron-Cash@9a29017c5d8906bb04f7e188bf483b0d3ff698f4

contrib/build-linux/appimage/build.sh

@@ -132,10 +132,10 @@ info "preparing electrum-locale."
 
 info "installing electrum and its dependencies."
 mkdir -p "$CACHEDIR/pip_cache"
-"$python" -m pip install --cache-dir "$CACHEDIR/pip_cache" -r "$CONTRIB/deterministic-build/requirements.txt"
-"$python" -m pip install --cache-dir "$CACHEDIR/pip_cache" -r "$CONTRIB/deterministic-build/requirements-binaries.txt"
-"$python" -m pip install --cache-dir "$CACHEDIR/pip_cache" -r "$CONTRIB/deterministic-build/requirements-hw.txt"
-"$python" -m pip install --cache-dir "$CACHEDIR/pip_cache" "$PROJECT_ROOT"
+"$python" -m pip install --no-warn-script-location --cache-dir "$CACHEDIR/pip_cache" -r "$CONTRIB/deterministic-build/requirements.txt"
+"$python" -m pip install --no-warn-script-location --cache-dir "$CACHEDIR/pip_cache" -r "$CONTRIB/deterministic-build/requirements-binaries.txt"
+"$python" -m pip install --no-warn-script-location --cache-dir "$CACHEDIR/pip_cache" -r "$CONTRIB/deterministic-build/requirements-hw.txt"
+"$python" -m pip install --no-warn-script-location --cache-dir "$CACHEDIR/pip_cache" "$PROJECT_ROOT"
 
 
 info "copying zbar"