cmd/link: fallback to older minimum Windows target version on older C GNU toolchains

Setting Windows 10 as the minimum target version requires setting
the IMAGE_GUARD_SECURITY_COOKIE_UNUSED flag in the PE load config
directory, else the executable will fail to run.

When using an external linker that flag is set by defining a
_load_config_used symbol with the proper value. However, older versions
of the GNU toolchain do not associate the _load_config_used symbol with
the PE load config directory.

To work around this issue, we can fallback to the previous minimum
Windows target version if the external linker doesn't special-case the
_load_config_used symbol.

Change-Id: I36ac7a2968c3576ac788bf192e7614bbae35ad1f
Reviewed-on: https://go-review.googlesource.com/c/go/+/763960
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>

0 files changed, 0 insertions, 0 deletions