Do not keep the build.zig cache manifest file locked.
Do not keep the build.zig cache manifest file locked.

This allows to have multiple instances of `zig build` at the same
time. For example when you have a long running `zig build run` and
then want to run `zig build somethingelse`.

zig-lang/zig,raulgrell/zig,andrewrk/zig,zig-lang/zig,raulgrell/zig,andrewrk/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,raulgrell/zig