misc/wasm: add stub for fs.openSync for browsers
misc/wasm: add stub for fs.openSync for browsers

This stub is necessary so the time package can fail to load
the timezone files in a nice way. It transitively makes the
log package work in browsers.

Change-Id: I4d360df82989d9b40cd31bb4508a6d057534443e
Reviewed-on: https://go-review.googlesource.com/118977
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

josharian/go,CAFxX/go,akutz/go,josharian/go,akutz/go,nawawi/go,golang/go,CAFxX/go,josharian/go,golang/go,cloudflare/go,josharian/go,golang/go,golang/go,CAFxX/go,akutz/go,nawawi/go,nawawi/go,cloudflare/go,cloudflare/go,cloudflare/go,akutz/go,CAFxX/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go,akutz/go,josharian/go,nawawi/go,cloudflare/go,golang/go,CAFxX/go,CAFxX/go,akutz/go,akutz/go,cloudflare/go,cloudflare/go,josharian/go,nawawi/go,josharian/go,CAFxX/go,nawawi/go,nawawi/go,golang/go,josharian/go,golang/go,akutz/go