This commit fixes linking issue on macOS 11 BigSur by appending
a prefix path to all lib and framework search paths known as
`-syslibroot`.
The reason this is needed is that in macOS 11, the system libraries
and frameworks are no longer readily available in the filesystem.
Instead, the new macOS ships with a built-in dynamic linker cache
of all system-provided libraries, and hence, when linking with either
`lld.ld64` or `ld64`, it is required to pass in `-syslibroot [dir]`.
The latter can usually be obtained by invoking `xcrun --show-sdk-path`.
With this commit, Zig will do this automatically when compiling natively
on macOS. However, it also provides a flag `-syslibroot` which can be
used to overwrite the automtically populated value.
To summarise, with this change, the user of Zig is not required to
generate and append their own syslibroot path. Standard invocations
such as `zig build-exe hello.zig` or `zig build` for projects will
work out of the box. The only missing bit is `zig cc` and `zig c++`
since the addition of the `-syslibroot` option would be a mismatch
between the values provided by `clang` itself and Zig's wrapper.
Fallback to sysctl `kern.osversion` when `kern.osproductversion` is not
available (prior to 10.13.4) .
The mapping from `sw_vers -buildVersion` to `-productVersion` is
formulaic from 10.8 to 10.15 and older is handled with switch.
closes#5119
Add std.Target.Cpu.Model.generic which is even more empty than baseline.
CPU model and feature detection uses this rather than baseline.
Rename cpu_detected to cpu_detection_unimplemented and flip the logic.
It can be relied on by stage2.zig to decide whether the LLVM workaround
is needed without also checking the CrossTarget.
Move the CPU detection to after the OS detection, and use the detected
OS for the CPU detection. This is relevant because operating systems
sometimes emulate certain CPU features, so knowing the OS and version is
relevant for determining CPU features.
Prepare for #4592 by passing the CPU arch to the detection code, instead
of having it rely on Target.current.
The CPU model & feature detection logic is modified. Before:
* Detect actual features
* Use as hint when detecting CPU model
* Populate dependencies of CPU model features
* Merge that into the actual features set
After:
* Detect actual features
* Use as hint when detecting CPU model
* Add known CPU model features to actual features
* Detect actual features again, overriding known CPU model features
* Populate dependencies
