PAGESIZE is actually the version defined in POSIX base, with PAGE_SIZE
being in the XSI option. use PAGESIZE as the underlying definition to
facilitate making exposure of PAGE_SIZE conditional.
linux, gcc, etc. all use "sh" as the name for the superh arch. there
was already some inconsistency internally in musl: the dynamic linker
was searching for "ld-musl-sh.path" as its path file despite its own
name being "ld-musl-superh.so.1". there was some sentiment in both
directions as to how to resolve the inconsistency, but overall "sh"
was favored.