Building Boost for ARM iOS simulator builds for iPhone

[Stannieman]

Describe the bug
When building Boost for the ARM iOS simulator it still builds for iPhone.

Environment

• OS: macOS Monterey (12.6)
• Compiler: Apple Clang 13.1.6

To Reproduce
Steps to reproduce the behavior:

1. Create a custom triplet that looks like this

set(VCPKG_TARGET_ARCHITECTURE arm64)
set(VCPKG_CRT_LINKAGE dynamic)
set(VCPKG_LIBRARY_LINKAGE static)
set(VCPKG_CMAKE_SYSTEM_NAME iOS)
set(VCPKG_OSX_SYSROOT iphonesimulator)

2. Install Boost in your project.
3. The Boost static libs are built for iphoneos.
4. The Boost libs cannot be linked with your own lib because Boost is built for iphoneos and your code is built for iphonesimulator.

Expected behavior
The Boost static libs are built for iphonesimulator and linking works.

Failure logs
ld: in /somethingSomething/build/ios-simulator-arm64-debug/vcpkg_installed/arm64-iossimulator13.7/debug/lib/libboost_thread.a(thread.o), building for iOS Simulator, but linking in object file built for iOS

Additional context
Other libs build correctly for the ARM64 simulator so I think the triplet is correct.
I suspect that VCPKG_OSX_SYSROOT is not passed to b2 or that b2 ignores it.
Unfortunately I have zero experience with b2 so I hope someone is able to give some hints.

[MonicaLiu0311]

This issue hasn’t been updated in 3 month, if it is still an issue, please reopen this issue.