libvorbis build error on macOS 14 / Xcode 15

[Thomas Nyman]

libvorbis-1.3.7 fails to build on macOS 14 due to changes to ld64 linker in Xcode 15.

Tested on:

• macOS 14.3.1 23D60 arm64
• Xcode 15.2 15C500b

./libraries/osx/build-osx-libs fails with:

ld: unknown options: -force_cpusubtype_ALL 
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[3]: *** [test_sharedbook] Error 1
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [all-recursive] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2
ERROR: libvorbis build failed

This is caused by the -force_cpusubtype_ALL flag being passed by the libvorbis configure script unconditionally for macOS builds (​https://gitlab.xiph.org/xiph/vorbis/-/blob/master/configure.ac#L205) even though the flag is only valid for PowerPC. Prior to Xcode 15 the ld64 linker silently ignored the flag for x86_64 and arm64 builds, but since Xcode 15 the linker now issues the above error.

There is an upstream bug report files with no resolution (​https://gitlab.xiph.org/xiph/vorbis/-/issues/2348) but since PowerPC doesn't appear to be a relevant target a possible resolution is to simply patch away the offending flag from the libvorbis configure script (see attached patch-vorbis-flags.diff).

The same approach is taken by macports when building the libvorbis port on affected architectures: ​https://github.com/macports/macports-ports/commit/e63376b0845acdc06efbfb5fbbb8bdd6359e75b4

[Thomas Nyman]

Patch to build-osx-libs.sh that removes the offending flags from libvorbis-1.3.7 configure