I have been having a very similiar bug to one reported elsewhere but not directed at musl at the time. It appears there was a issue with the user.h header in the past that returned trad-core page size errors as well. Has this bug made its way into the musl user.h header ? If there is anything i can provide to assist please let me know.

/binutils/bfd/trad-core.c: In function 'trad_unix_core_file_p':
trad-core.c:118: error: 'PAGE_SIZE' undeclared (first use in this function)
trad-core.c:118: error: (Each undeclared identifier is reported only once
trad-core.c:118: error: for each function it appears in.)

https://sourceware.org/bugzilla/show_bug.cgi?id=5145

thanks,

stephen