Build for iOS Simulator on arm64

[tsouza]

I've been researching how to build nodejs-mobile for running on iOS Simulator for arm64. My first attempt was modifying the ios build scripts so it would only build nodejs with --dest-os=ios --dest-cpu=arm64 and then build both frameworks (iphoneos and iphonesimulator) with -arch arm64. But my attempt failed at ld command for -arch arm64 -sdk iphonesimulator with an error that did not make much sense saying that the nodejs lib*.a were built for iOS instead of iOS Simulator.

So after more research it turns out we can simply transform the binary built for iphone on arm64 into iphonesimulator arm64. The command was taken from this great article:

$ xcrun vtool -arch arm64 \
              -set-build-version 7 11.0 11.0 \
              -replace \
              -output NodeMobile.framework/NodeMobile.iphonesimulator \
              NodeMobile.framework/NodeMobile

Which produces a new binary that will run in iOS Simulator on arm64. I can confirm this is at least working for me (I am building a swift library on top of nodejs mobile)

I can open a PR with the necessary changes. I think we can use lipo to build a version of NodeMobile for both x86_64 and arm64.

[staltz]

Thanks for the tip! I'll try this myself, and indeed, I have once used vtool to hack the headers of the binary, and it works. I'll look into incorporating this into the nodejs-mobile scripts too, but hopefully in a manner that still supports x64 MacOS hosts.