First stage of cleanup in source tree pollution

[sbc100]

Update build-js.sh to output to out directory. This is district
from the bin directory which is used by the cmake build and may or
may not live in the source tree. The out directory currently always
lives in the source tree.

As a followup change I hope to additionally move all test outout into
this tree.

See #2104

[kripken]

Why not keep using bin/ for the js output, even if cmake happens to point to somewhere else?

[sbc100]

I was a little confusing because BINARYEN_BIN is in the output directory (i.e. not necessarily under the source checkout at all). But the build-js.sh always writes into the source directory.

I'm using "out" as place where all kind of intermiates can be written, and "bin" as the place where the final binaries live. In a followup I'm trying to have all tests write to the "out" directory too.

[dschuff]

In general I like the idea.

[dschuff]

what is the effect of adding the leading / everywhere?

[sbc100]

IIUC is just makes it a more precise match.

e.g.

*.o

vs

/*.o

The latter only match objects at the top level

[kripken]

Sounds reasonable. I slightly worry because emcc does look at $BINARYEN_ROOT/bin for wasm-opt, wasm2js, etc. I guess we can update that if necessary?

[sbc100]

Those tools still build to "bin" and install to "bin". But for out-of-tree build the "bin" the build to is $BUILDDIR/bin.

i'm not changing to locations of any of the cmake targets.. Only the build-js target

[kripken]

That should be fine then - I don't think we depend on the location of binaryen.js anymore anywhere.