[CI] devtool: Use ramdisk for TMPDIR

Currently some tests are failing when running `devtool test` using a
ramdisk, because they are trying to create hard links between `/srv`
(which is inside the ramdisk) and `/tmp` (which is not). However,
cross-device hard links are not allowed.

When running with a ramdisk make `$TMPDIR` point to a directory inside
it.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Author: bchalios

tools/devtool

@@ -1251,7 +1251,7 @@ cmd_test() {
 
     if [[ $ramdisk = true ]]; then
         mount_ramdisk ${ramdisk_size}
-        ramdisk_args="--volume ${DEFAULT_RAMDISK_PATH}:${DEFAULT_TEST_SESSION_ROOT_PATH}"
+        ramdisk_args="--env TMPDIR=${DEFAULT_TEST_SESSION_ROOT_PATH}/tmp --volume ${DEFAULT_RAMDISK_PATH}:${DEFAULT_TEST_SESSION_ROOT_PATH}"
     fi
 
     # Testing (running Firecracker via the jailer) needs root access,