An error with the --single-threaded option on build

[ohno418]

In the "Zig competes with C instead of depending on it" section on the "In-depth Overview" page, the following command causes an error:

$ zig build-exe hello.zig -O ReleaseSmall --strip --single-threaded
error: unrecognized parameter: '--single-threaded'

I'm new to ziglang and not sure if I'm missing something, so just reporting.

version:

$ zig version --help
0.9.1