Building on MacOS11 tries to use SDK for MacOS12

[RenaudFondeur]

When building the objective C files during the VM build, cmake by default tried to use the MacOS12 SDK, failing compilation.

We worked it around by explicitly setting -DCMAKE_OSX_SYSROOT=... as specified here: https://stackoverflow.com/questions/10165335/can-cmake-specify-the-base-sdk-on-mac-os-x.

We also saw that CMake provides already support to detect the SDK and that we should use https://cmake.org/cmake/help/latest/variable/CMAKE_OSX_DEPLOYMENT_TARGET.html#variable:CMAKE_OSX_DEPLOYMENT_TARGET
to specify the target instead of setting the compiler flag manually like this

pharo-vm/CMakeLists.txt

Line 263 in 48ddfee

set(COMMON_FLAGS "-stdlib=libc++ -mmacosx-version-min=10.7 ${COMMON_FLAGS}")

.

Otherwise CMake can override it and provoke this issue

[guillep]

@RenaudFondeur I fixed this in the last PR, would you mind if this works out of the box in your machine?

[guillep]

(you will need to pull)