TLDR: This updates our macOS toolchain to use a newer version of Clang, cctools (including new dependency on libtapi), LD64 and the macOS SDK.
I’ve been testing depends builds (HOST=x86_64-apple-darwin16) inside a Debian Buster Docker container, and running the resultant bitcoind and bitcoin-qt binaries on a macOS 10.14.4 system. The .dmg generated by a make deploy also mounts correctly on the same macOS system.
Clang
Upgraded from 3.7.1 to 6.0.1
cctools
See tpoechtrager/cctools-port and tpoechtrager/apple-libtapi.
macOS SDK
Upgraded from building against the macOS 10.11 SDK to the macOS 10.14 SDK.
TODO
-  Make the 10.14SDK available to Travis.