https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87030
--- Comment #4 from Jack Howarth <howarth.at.gcc at gmail dot com> --- A couple notes here. 1) As I mentioned in the duplicate PR 87257, Apple achieved the obsoleting of the i386 support in Xcode 10 through the libSystem.tbd in the 10.14 SDK's buried /usr/lib/libSystem.tbd which only exposes the x86_64 symbols from the root level /usr/lib/libSystem.dylib. So one could hack continued support for i386 in for awhile more if gcc replaced its -lSystem linkage with an explicit /usr/lib/libSystem.dylib linkage. 2) Since the default behavior for the command line tools from Xcode 10 are to not install the SDK in the root directory, the gcc compiler needs to be bootstrapped with--with-sysroot=$SDK_PATH to build under Xcode 10 on 10.14. This issue doesn't exist on 10.13 which still installs the system headers in the root directory.
