gotest: don't use local

It's not part of the POSIX shell standard.

Change-Id: I1b09b3166e50bb8814f36476d4e5aeb925721495
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/214300
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/libgo/testsuite/gotest b/libgo/testsuite/gotest
index 4293db9..6929de3 100755
--- a/libgo/testsuite/gotest
+++ b/libgo/testsuite/gotest
@@ -538,8 +538,7 @@
 # Takes an example name and puts any output into the file example.txt.
 # It strips comment markers but does not otherwise change the output.
 exampleoutput() {
-    local n=$(testname $1)
-    local f
+    n=$(testname $1)
     for f in $gofiles $xgofiles; do
 	if ! grep "^func $n(" $f >/dev/null 2>&1; then
 	    continue