Fix test_compiler_cache

We need exactly 1 binary for the fake ccache wrapper.
So change the sed to skip the first line (wrapper) and print the 2nd, then stop.

Avoids issues when there is e.g. /usr/bin/gcc and /usr/local/bin/gcc

test/framework/toolchain.py

@@ -2326,8 +2326,8 @@ def test_compiler_cache(self):
                 "#!/bin/bash",
                 "echo 'This is a %s wrapper'" % cache_tool,
                 "NAME=${0##*/}",
-                "comm=$(which -a $NAME | sed 1d)",
-                "$comm $@",
+                "comm=$(which -a $NAME | sed -n 'n;p')",
+                '$comm "$@"',
                 "exit 0"
             ]
             script = '\n'.join(txt)