[release-branch.go1.1] cmd/gc: repair make(T) in export data for inlining.

««« CL 9303050 / 9a73efa2cd4e
cmd/gc: repair make(T) in export data for inlining.

When T was an unexported type it could be forgotten.

Fixes #5470.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/9303050
»»»

R=bradfitz, iant, remyoudompheng
CC=golang-dev
https://golang.org/cl/10029043