Please check the build logs for more information.
See Builds for ideas on how to fix a failed build, or Metadata for how to configure docs.rs builds.
If you believe this is docs.rs' fault, open an issue.
Rust Cross has a good explanation of how cross-compiling Rust works in general. While the author of Rust Cross advises against it, it is perfectly possible to cross-compile Rust for MacOS on Linux. OSXCross can be used to create a compiler toolchain that can compile for MacOS on Linux.
When cross-compiling for MacOS on Linux there are two environment variables that are used to configure how
coreaudio-sys finds the required headers and libraries. The following examples assume that you have OSXCross installed at
coreaudio-sys where to find the MacOS SDK: