cmd/link: improve error for missing SDYNIMPORT support on mips/mips64
Issue an error (instead of crashing) when encountering a symbol that
requires dynamic relocations on mips/mips64. The dynimport support is
in progress, but is not done yet, so rather than crashing, print a
message indicating that the feature is not yet implemented and exit.
Fixes #58240.
Change-Id: I9ad64c89e4f7b4b180964b35ad1d72d375f2df7f
Reviewed-on: https://go-review.googlesource.com/c/go/+/466895
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Joel Sing <joel@sing.id.au> Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>