Restrict in memory mmap arguments to glibc on s390x

[jogemu]

DirectMmap fails for musl, because passing mmap arguments in memory is glibc specific.

[mkruskal-google]

What about this code fails for musl? I'm not seeing something glibc-specific here

[jogemu]

low_level_alloc.cc uses DirectMmap during runtime

abseil-cpp/absl/base/internal/low_level_alloc.cc

Lines 588 to 589 in 3e0d9ff

	new_pages = base_internal::DirectMmap(nullptr, new_pages_size,
	PROT_WRITE|PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);

which returns MAP_FAILED with EINVAL

abseil-cpp/absl/base/internal/low_level_alloc.cc

Lines 598 to 599 in 3e0d9ff

	if (new_pages == MAP_FAILED) {
	ABSL_RAW_LOG(FATAL, "mmap error: %d", errno);

[low_level_alloc.cc : 599] RAW: mmap error: 22 occurred during nodejs snapshot generation, which uses an older version that is permalinked above.

In musl mmap syscalls behave consistently with other 64-bit architectures, due to this condition: if (n == SYS_mmap) return __syscall1(n, (long)(long[]){a,b,c,d,e,f}); https://git.musl-libc.org/cgit/musl/tree/arch/s390x/syscall_arch.h#n64

Just for the s390x architecture, glibc still uses old_mmap to maintain backward compatibility.