testing: style change: omit unnecessary new

This was brought to my attention because a user thought that because
the file was named "example.go" it served as an example of good coding
practice.  It's not an example, of course, but may as well use a more
idiomatic style anyhow.

Change-Id: I7aa720f603f09f7d597fb7536dbf46ef09144e28
Reviewed-on: https://go-review.googlesource.com/1902
Reviewed-by: Minux Ma <minux@golang.org>
cmd/cgo: don't #include cgo_export.h in gccgo _cgo_main.c

Instead of relying on the asm names declared in the gccgo version of
cgo_export.h, just emit a dummy symbol with the right asm name.  This
is enough to let the _cgo_main link succeed, which is all that matters
here.

Fixes #9294.

Change-Id: I803990705b6b226ed0adf17dc57b58a9f501b213
Reviewed-on: https://go-review.googlesource.com/1901
Reviewed-by: Minux Ma <minux@golang.org>