Add get-task-allow entitlement to allow debuggers to attach to code…

…signed Julia (JuliaLang#37069)

Without this entitlement, users that wish to attach a debugger to the
codesign Julia executable they receive from `julialang.org` must strip
the codesigning signature from the Julia executable (e.g. via `codesign
--remove-signature Julia-1.5.app/Contents/Resources/bin/julia`).  This
has its disadvantages, of course, so much better to simply declare to
the OS that it's alright for other processes to attach to this process.

contrib/mac/app/Entitlements.plist

@@ -4,6 +4,8 @@
 <dict>
  <key>com.apple.security.automation.apple-events</key>
  <true/>
+ <key>com.apple.security.cs.get-task-allow</key>
+ <true/>
  <key>com.apple.security.cs.allow-dyld-environment-variables</key>
  <true/>
  <key>com.apple.security.cs.allow-jit</key>