build: add a deterministic dmg signer

Makefile.am

@@ -26,7 +26,9 @@ WINDOWS_PACKAGING = $(top_srcdir)/share/pixmaps/bitcoin.ico \
 
 OSX_PACKAGING = $(OSX_DEPLOY_SCRIPT) $(OSX_FANCY_PLIST) $(OSX_INSTALLER_ICONS) \
   $(top_srcdir)/contrib/macdeploy/background.png \
-  $(top_srcdir)/contrib/macdeploy/DS_Store
+  $(top_srcdir)/contrib/macdeploy/DS_Store \
+  $(top_srcdir)/contrib/macdeploy/detached-sig-apply.sh \
+  $(top_srcdir)/contrib/macdeploy/detached-sig-create.sh
 
 COVERAGE_INFO = baseline_filtered_combined.info baseline.info block_test.info \
   leveldb_baseline.info test_bitcoin_filtered.info total_coverage.info \