shell: Fail if building --with-libedit and can't find libedit

Previously, configure --with-libedit would only fail in the case where
libedit is available but its header file histedit.h is not.

Fixes: 13537aaa484b ("[BUILD] Added --with-libedit option to...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
1 file changed