Fixes https://github.com/denoland/deno/issues/25862.
npm only makes bin entries executable if they get linked into `.bin`, as
we did before this PR. So this PR actually deviates from npm, because
it's the only reasonable way to fix this that I can think of.
---
The reason this was broken in moment is the following:
Moment has dependencies on two typescript versions: 1.8 and 3.1
If you have two packages with conflicting bin entries (i.e. two
typescript versions which both have a bin entry `tsc`), in npm it is
non-deterministic and undefined which one will end up in `.bin`.
npm, due to implementation differences, chooses to put typescript 1.8
into the `.bin` directory, and so `node_modules/typescript/bin/tsc` ends
up getting marked executable. We, however, choose typescript 3.2, and so
we end up making `node_modules/typescript3/bin/tsc` executable.
As part of its tests, moment executes `node_modules/typescript/bin/tsc`.
Because we didn't make it executable, this fails.
Since the conflict resolution is undefined in npm, instead of trying to
match it, I think it makes more sense to just make bin entries
executable even if they aren't chosen in the case of a conflict.
