We're using musl in multiarch/multilib setup (i386/x86-64) and it works fine, except for header duplication. Given two architectures, i386-linux-gnu and x86_64-linux-gnu, I'd like to install the shared headers into /usr/include, and install bits (what is normally in include/bits) for each architecture into the respective subfolders /usr/include/i386-linux-gnu/bits and /usr/x86_64-linux-gnu.

I can obviously achieve by copying/moving files after install, but I'd prefer to have the support for that scenario directly in the Makefile. Would you accept such patch?

There are two possible ways to implements this I can think of: (1) add a separate targets such as install-arch-headers and install-generic-headers, or (2) define additional Makefile variable such as includebits which would be set to $(includedir)/bits by default but could be overridden when invoking make. Do you have strong preference for either of these solutions?