When building windows/386 executable that imports "plugin" package,
cmd/link adds reference to DLL with blank name. Running

objdump -x a.exe

reports

...
The Import Tables (interpreted .idata section contents)
...
DLL Name:
vma:  Hint/Ord Member-Name Bound-To
25308a     0  _GLOBAL_OFFSET_TABLE_
...

So, obviously, executable cannot run, because Windows complains
that it cannot find DLL when trying to run it.

Stop using _GLOBAL_OFFSET_TABLE_ on windows/386.

Fixes #28789

Change-Id: Idd489eafd998f6e329f40c5d90a2a8965ab1d873
Reviewed-on: https://go-review.googlesource.com/c/151139
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>