cmd/cgo: use objdir consistently, create it as needed

Previously we added a slash to the end of objdir only after
processing input files. The effect was that the temporary gcc
output files were placed in /tmp, using objdir as a prefix.
Those output files were not removed by anything.

Now we consistently use objdir as a directory, not a prefix.
We only create it when needed; there is already a test for that in
cmd/go/testdata/script/build_cwd_newline.txt.

Change-Id: Ie66d9c04ecc3c0f5950fc1111c74e1d01c67304c
Reviewed-on: https://go-review.googlesource.com/c/go/+/740742
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

0 files changed, 0 insertions, 0 deletions