Support ARM64 macOS builds

[DarkDust]

This provides basic support for building OpenSSL on macOS for ARM64 as well.

This pull request needs to make a number of changes:

• First, a check whether to actually compile for macOS ARM64 is made, based on the SDK version.
  • This is not completely correct right now as Apple provides two Xcode 12 betas, one with macOS ARM64 support and one without. But the final Xcode release is going to be just one Xcode build which supports everything.
• The build directories and logs, which previously were only differentiated by architecture, now also include the OS in their names (e.g. 1.0.2u-MacOSX-arm64.build.log) since there are now two (or three) OSs which build for ARM64.
• While I was at it, I also split up the log files into .config. and .build. so that the later doesn't overwrite the former any more.
• There's no darwin64-arm64-cc target in OpenSSL, but iphone-cross seems to work just fine when given the macOS SDK.
• The macOS build process has been moved into build() and that function was refactored a bit.
• build()'s second argument is now repurposed (and renamed) to OS as the SDK wasn't needed at that point any more, but OS was.
• I needed to introduce a config file for Xcode, OpenSSL.xcconfig, to work around a current limitation in Xcode 12 beta (see below).

Known issues/limitations

• Xcode 12 beta does not support building iPhoneSimulator for ARM64 yet.
  • The build script has a dedicated variable BUILD_IPHONESIMULATOR_ARM64 because of that. It's currently never set, once Xcode does support building iPhoneSimulator for ARM64 we can set it.
  • However, we would need to solve a conflict in the headers between iOS ARM64 and iPhoneSimulator ARM64 then. Haven't bothered to do this yet since it's possible Apple never support iPhoneSimulator ARM64 since ARM-based Macs are going to be able to run iOS apps natively.
  • Xcode needs to be told not to try to link iPhoneSimulator ARM64. That's what the OpenSSL.xcconfig is for.
• In my builds, the iOS libcrypto.a and libssl.a contain the armv7s architecture, but the final OpenSSL.framework does not. I don't know why, yet.
• Xcode 12 only supports minimum deployment targets of iOS 9.0 (IIRC) and macOS 10.9. The binaries do contain the entries for iOS 8.0 and macOS 10.8 but it might be a good idea to raise the deployment targets in the project and podspec.

[DarkDust]

Correction: The frameworks produced with Xcode 12 beta do have the minimum deployment targets set to iOS 8.0 and macOS 10.9, even though iOS 6.0 and macOS 10.8 were passed to the compiler (which, funnily enough, is visible inside the final binaries).

[krzyzanowskim]

this is fantastic! I'll back to it ASAP

[krzyzanowskim]

@DarkDust just to clarify. With these changes, does it still build with Xcode 11?

[krzyzanowskim]

Something is off with result. After I run the script, macos result is missing

./build.sh
Building for iPhoneSimulator i386
Configuring for iPhoneSimulator.platform i386
Building /var/folders/2_/tt78sncj6p9fbmkn7808254h0000gn/T/tmp.2dMv5WRe/1.0.2u-iPhoneSimulator-i386.build.log
Building for iPhoneSimulator x86_64
Configuring for iPhoneSimulator.platform x86_64
Building /var/folders/2_/tt78sncj6p9fbmkn7808254h0000gn/T/tmp.2dMv5WRe/1.0.2u-iPhoneSimulator-x86_64.build.log
Building for iPhoneOS armv7
Configuring for iPhoneOS.platform armv7
Building /var/folders/2_/tt78sncj6p9fbmkn7808254h0000gn/T/tmp.2dMv5WRe/1.0.2u-iPhoneOS-armv7.build.log
Building for iPhoneOS armv7s
Configuring for iPhoneOS.platform armv7s
Building /var/folders/2_/tt78sncj6p9fbmkn7808254h0000gn/T/tmp.2dMv5WRe/1.0.2u-iPhoneOS-armv7s.build.log
Building for iPhoneOS arm64
Configuring for iPhoneOS.platform arm64
Building /var/folders/2_/tt78sncj6p9fbmkn7808254h0000gn/T/tmp.2dMv5WRe/1.0.2u-iPhoneOS-arm64.build.log
Building for MacOSX x86_64
Configuring for MacOSX.platform x86_64
Building /var/folders/2_/tt78sncj6p9fbmkn7808254h0000gn/T/tmp.iHj3nIE5/1.0.2u-MacOSX-x86_64.build.log

[DarkDust]

Oh, sorry, I‘ll look into this tomorrow.

[DarkDust]

I found the problem: even though the SDK version is 10.15.4, the SDK path is .../Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk (note the missing .4). I've changed the derivation of CROSS_TOP and CROSS_SDK (used by the OpenSSL configure/makefile) to derive it from the actual SDK path instead.

This means we don't need the *_SDK_VERSION and *_PLATFORM variables any more (except for OSX_SDK_VERSION to decide whether to build for ARM64).

The updated version now builds both with Xcode 11 and 12 beta.

[krzyzanowskim]

@DarkDust thank you!