Sometimes asm code in 2 different packages name its global
symbols with the same name. When these symbols are passed
to gcc, it refuses to link them thinking they are duplicate.
Mark these symbols with IMAGE_SYM_CLASS_STATIC.

Fixes #19198.

Change-Id: Ia5f59ede47354a2b48ce60b7d406c9f097ff2000
Reviewed-on: https://go-review.googlesource.com/37810Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>