The command of install could not handle the special files in exec
testcases, change the default rule to rsync to fix this.

The installation is unchanged after this commit.
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>