Support createdump functionality in the app sandbox

[rolfbjarne]

The 'createdump' tool doesn't currently work in the app sandbox (i.e. when publishing to the App Mac Store).

Ref: dotnet/macios#16189

Making it work as a standalone executable has numerous challenges:

• createdump has to be signed with a bundle identifier. It doesn't seem like the same bundle identifier as the main app can be used, although I wasn't able to confirm this (in any case it sounds like a bad idea to re-use the bundle identifier).
• createdump requires a few custom entitlements: https://github.com/dotnet/runtime/blob/main/eng/pipelines/common/createdump-entitlements.plist
• createdump would also need the sandbox entitlement to publish to the App Store (com.apple.security.app-sandbox).
• I'm not entirely sure whether a custom provisioning profile is required. If so, createdump would have to be put inside an app-like directory structure: https://developer.apple.com/documentation/Xcode/signing-a-daemon-with-a-restricted-entitlement. This is inconvenient, because CoreCLR expects createdump next to one of its dylibs. Maybe this can be worked around with a symlink?
• It seems that since a bundle identifier is required, an Info.plist must be embedded inside the executable, which is done when the executable is linked (by passing -sectcreate __TEXT __info_plist path/to/Info.plist to ld)... but we get the executable already linked from the runtime pack.

Also interesting: https://developer.apple.com/documentation/xcode/embedding-a-helper-tool-in-a-sandboxed-app

An alternative approach seems to be to embed the createdump functionality as a static library, and then potentially fork before generating the dump. This is apparently what .NET does for single-file executables.

Ref: #84864
Ref: #89203
Ref: https://discord.com/channels/732297728826277939/732297808148824115/1149344656480550912

In any case, we don't even know if there's community interest in supporting createdump functionality in the app sandbox, so if you're interested, please upvote this issue. If we get enough interest, we'll look into it, otherwise we'll eventually close this issue.

[rolfbjarne]

Fixing dotnet/macios#23848 would probably make this trivial to fix.

[steveisok]

Can you transfer this over to runtime? We're going to look at this generally as part of consolidation.

[rolfbjarne]

@steveisok note that this is only applicable to macOS and Mac Catalyst apps, iOS and tvOS apps aren't allowed to execute other executables.