Detect common misconfigurations on error

[madsmtm]

It is fairly common when cross-compiling to:

• Try to use GCC configured for the host system.
• Not have headers for the target system.

It would be nice if cc-rs could detect this (maybe by inspecting the error message), and give an extra note in those cases that guides the user in what they need to do.

(This is only one part of the cross-compilation story; a linker and libraries / linker stubs are also necessary, but that should be up to rustc to detect and warn for such incompatibilities).