Issue 5013: Fix scripts for environments where "set -ux" carries over

Issue 5013: Fix scripts for environments where "set -ux" carries over

Normally, in Bourne shell scripts,
"set -ux" does not carry over to child processes.
However, under some conditions, it carries over to child processes.
(E.g. environment variable SHELLOPTS exists.)

If "set -ux" in smart-autogen.sh carries over to the child processes,
autoconf fails.

In order to avoid the issue,
this commit makes smart-autogen.sh and smart-configure.sh use
"set +ux" to cancel the effect of "set -ux"
just before invoking the child process.

Likewise, this commit also removes "set -e"
for avoiding "set -e" carrying over, and adds alternative error handling.