configure: Be more verbose when compiler sanity checks fail

When configure could not get past initial compiler sanity check
the user was left with no explanation why this happened (usually
the reason is that compilers are not installed).

By printing the executed command line and re-executing it without
output redirection user gets better information how to proceed
(or ask for help) to resolve this problem.

The shell builtin 'printf' is used to print the executed command
line to ensure verbatim output.