Go 1.15.8 breaks Windows builds

After upgrading to Go 1.15.8, the Windows builds are broken with errors like

C:\Users\Administrator\cbdepscache\exploded\amd64\go-1.15.8\go\pkg\tool\windows_amd64\link.exe: running gcc failed: exit status 1 

C:/ProgramData/chocolatey/lib/mingw/tools/install/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.1.0/../../../../x86_64-w64-mingw32/bin/ld.exe: Error: export ordinal too large: 77640

This appears to be caused by https://github.com/golang/go/issues/43591 which is scheduled to be fixed in Go 1.15.9 or Go 1.15.10, and should not affect earlier or later 1.x versions.

A workaround for the moment is to add -buildmode=exe to the go build command. We may wish to remove this later when we can upgrade to a Go version without this problem.