mac build: log hash of .app for quick checking of build-repro

I think that hash should match between unsigned and release builds,
as the codesigning/notarisation is done right after.

contrib/osx/make_osx.sh

@@ -244,6 +244,9 @@ VERSION=$(git describe --tags --dirty --always)
 info "Building binary"
 ELECTRUM_VERSION=$VERSION pyinstaller --noconfirm --ascii --clean contrib/osx/osx.spec || fail "Could not build binary"
 
+info "Finished building unsigned dist/${PACKAGE}.app. This hash should be reproducible:"
+find "dist/${PACKAGE}.app" -type f -print0 | sort -z | xargs -0 shasum -a 256 | shasum -a 256
+
 DoCodeSignMaybe "app bundle" "dist/${PACKAGE}.app"
 
 if [ ! -z "$CODESIGN_CERT" ]; then