cmd/cgo: avoid exporting all symbols on windows buildmode=c-shared
Disable default symbol auto-export behaviour by marking exported
function with the __declspec(dllexport) attribute. Old behaviour can
still be used by setting -extldflags=-Wl,--export-all-symbols.
See https://sourceware.org/binutils/docs/ld/WIN32.html for more info.
This change cuts 50kb of a "hello world" dll.
Updates #6853
Fixes #30674
Change-Id: I9c7fb09c677cc760f24d0f7d199740ae73981413
Reviewed-on: https://go-review.googlesource.com/c/go/+/262797
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Trust: Alex Brainman <alex.brainman@gmail.com>