Tweak `MAP_SYNC`

src/unix/linux_like/linux/gnu/b32/arm/mod.rs

src/unix/linux_like/linux/gnu/b32/powerpc.rs

src/unix/linux_like/linux/gnu/b32/sparc/mod.rs

src/unix/linux_like/linux/gnu/b32/x86/mod.rs

src/unix/linux_like/linux/gnu/b64/aarch64/mod.rs

src/unix/linux_like/linux/gnu/b64/powerpc64/mod.rs

src/unix/linux_like/linux/gnu/b64/riscv64/mod.rs

src/unix/linux_like/linux/gnu/b64/sparc64/mod.rs

src/unix/linux_like/linux/gnu/b64/x86_64/mod.rs

src/unix/linux_like/linux/mod.rs

src/unix/linux_like/linux/musl/b32/arm/mod.rs

src/unix/linux_like/linux/musl/b32/x86/mod.rs

src/unix/linux_like/linux/musl/b64/aarch64/mod.rs

src/unix/linux_like/linux/musl/b64/powerpc64.rs

src/unix/linux_like/linux/musl/b64/x86_64/mod.rs