refactor(expect): redirect post-LAVA Expect script output

This change dumps the result of the post-LAVA Expect script runs to
isolated files, which are artefacted, rather than to the console.

Some of these log files are quite large, so debugging from the console
is just unnecessarily painful.

Change-Id: I8f9e6c5334eebcc058cf0b1df654fd9a61334b90
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/script/expect-post-runner.sh b/script/expect-post-runner.sh
index cb12c85..4f3ab68 100755
--- a/script/expect-post-runner.sh
+++ b/script/expect-post-runner.sh
@@ -51,7 +51,7 @@
 
         export uart_log_file="${WORKSPACE}/lava-${uart}.log"
 
-        expect "${expscript}"
+        2>&1 expect "${expscript}" > "${WORKSPACE}/lava-${uart}-expect.log"
     )
 
     if [ $? != 0 ]; then