Compiler fails to search “/usr/local/include” after updating to macOS Mojave

问题

After updating to macOS Mojave, the the OS fails to search for headers in /usr/local/include when compiling with clang++ (from the command-line, i.e. outside Xcode). Note that /usr/local/include is for my system the default paths in which CMake installs the headers, it thus feels quite strange of having to manually include this.

Incidentally I have also performed a clean install, resulting in the same problem. In the latter I have, in the following order:

1. Installed Xcode from the App-store.
2. Ran xcode-select --install.

The problem appears to be similar as in this question where it is suggested to:

• Run xcode-select --install. This obviously does not solve the problem. Insisting on this by rerunning the install command results in error: command line tools are already installed.
• Then there is the suggestion to check the output of xcode-select -p. It should apparently read /Library/Developer/CommandLineTools, not /Applications/Xcode.app/Contents/Developer as in my case. The suggestion is to "delete [sic] Xcode from the Applications directory", which seems to be a bit brutal.

How to solve this?

来源：https://stackoverflow.com/questions/52519492/compiler-fails-to-search-usr-local-include-after-updating-to-macos-mojave