wasm32-unknown-unknown target should not make output executable

[joshtriplett]

The wasm32-unknown-unknown target sets the executable bit on the compiled .wasm file. Most uses of wasm don't execute the wasm file directly, and without special configuration (such as binfmt-misc on Linux), most operating systems can't directly run wasm files. Furthermore, the executable bit set on the output tends to get checked into git repositories.

For the wasm32-unknown-unknown target, we should not set the executable bit on the output file.

[lachlansneff]

I'm not sure I agree with this. A .wasm file does represent an executable, and there's no fundamental reason why operating systems couldn't have built-in support for webassembly in the future. Just as the executable bit is set on binaries created when cross-compiling, my opinion is that the same be set of webassembly binaries.

[joshtriplett]

It does represent an executable, but not necessarily one for the host platform.