Catch2 does not compile with clang-8 on macOS

[torfinnberset]

Describe the bug
Catch2 does not compile with LLVM clang-8 on macOS. I get the following error message:

In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/sys/sysctl.h:83,
                 from /Users/torfinn/.conan/data/Catch2/2.7.0/catchorg/stable/package/5ab84d6acfe1f23c4fae0ab88f26e3a396351ac9/include/catch2/catch.hpp:8405,
                 from /Users/torfinn/.conan/data/<...>/stable/package/5926da2a8f608c60dbd4ba8eb9c5b650bd6fbdcb/src/main.cpp:18:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/sys/ucred.h:94:2: error: '_Atomic' does not name a type

Expected behavior
The program should compile with clang on macOS.

Reproduction steps
On macOS, install LLVM with brew install llvm.
Compile a main file with clang:

#define CATCH_CONFIG_MAIN
#include <catch2/catch.hpp>

Platform information:

• OS: macOS 10.14.3
• Compiler+version: Clang v8.0.0
• Catch version: v2.7.0
• XCode 10.2

Additional information
It seems clang doesn't like the macOS system header sys/sysctl.h. The program compiles just fine with AppleClang 10.0.1