tool_chain: check for various autoconf installs.

There exist different default setups for a specific autoconf version:
* autoconf
* autoconf$(VERSION)
* autoconf-$(VERSION)

As of now, only the second option is recognized by the check in tool_chain.

This patch ensures that if one of those is present in the correct
version, it will be found and used in the build process.

Fixes #1053.