[dev.boringcrypto] crypto/internal/boring: add -pthread linker flag
goboringcrypto_linux_amd64.syso references pthread functions, so
we need to pass -pthread to the C linker when external linking.
Usually it is automatically added when linking with runtime/cgo
package. But in shared linkage the runtime/cgo package may be in
a separate DSO and not part of this invocation.
Fixes #49965.
Change-Id: I3a9983e715ee804594a14006f212f76769ad71db
Reviewed-on: https://go-review.googlesource.com/c/go/+/369161
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Filippo Valsorda <filippo@golang.org>