macOS codesigning: only attempt if $MACOS_CODESIGN_IDENTITY is set (#…

…33228)

This has the following advantages:

* It allows our buildbots to pass in which code signing identity they
want to use (rather than having the identity hash hardcoded in our build
system)

* It stops blindly attempting to codesign on random user's machines

* It causes codesign failure to stop the build

(cherry picked from commit 0760842)

contrib/mac/app/Makefile

@@ -49,7 +49,12 @@ dmg/$(APP_NAME): startup.applescript julia.icns
  -mkdir -p $@/Contents/Resources/julia
  make -C $(JULIAHOME) binary-dist
  tar zxf $(JULIAHOME)/$(JULIA_BINARYDIST_FILENAME).tar.gz -C $@/Contents/Resources/julia --strip-components 1
- -codesign -s "AFB379C0B4CBD9DB9A762797FC2AB5460A2B0DBE" --deep $@
+ if [ -n "$$MACOS_CODESIGN_IDENTITY" ]; then \
+ echo "Codesigning with identity $$MACOS_CODESIGN_IDENTITY"; \
+ codesign -s "$$MACOS_CODESIGN_IDENTITY" -v --deep $@; \
+ else \
+ true; \
+ fi
 
 ROOTFILES := $(shell ls -ld dmg/*.app *.dmg 2> /dev/null | awk '{print $$3}')
 clean: