HN user
FWIW Nintendo's Horizon OS is also built from scratch (and isn't Unix at all), and has also shipped on a massive amount of units (over 110M as of 2022).
(and it happens to have a libcurl port)
Tried -fno-builtin-malloc on a hunch and it does seem to prevent the zero-initialisation logic from getting optimised away: https://godbolt.org/z/xWbEqcenn
musl probably uses -fno-builtin to disable any special handling of "builtin" library functions like malloc and memcpy?
Rosetta is faster than native in that case because the AArch64 JIT has to fall back to the interpreter for memchecks (unlike the x86-64 JIT).