Change error message when linking fails

I just lost half a day of work because the error message for linker failures is extremely misleading:

```
cabal: Missing dependency on a foreign library:
* Missing C library: chipmunk
This problem can usually be solved by installing the system package that
provides this library (you may need the "-dev" version). If the library is
already installed but in a non-standard location then you can use the flags
--extra-include-dirs= and --extra-lib-dirs= to specify where it is.
```

This suggests that the library isn't there, or at least not on cabals library search path. I had to turn on -v3 to find out that the problem wasn't that the library couldn't be found, but that it requires libm which wasn't linked to.

```
/usr/local/lib/libchipmunk.so: undefined reference to `__pow_finite'
/usr/local/lib/libchipmunk.so: undefined reference to `sincos'
/usr/local/lib/libchipmunk.so: undefined reference to `__exp_finite'
/usr/local/lib/libchipmunk.so: undefined reference to `sin'
/usr/local/lib/libchipmunk.so: undefined reference to `__acos_finite'
```

I suggest that upon failure to link the real error message (in this case, the one from gcc - I don't know what's being used on windows or osx) should _always_ be reported. In any case, an error message shouldn't give a wrong impression of what the actual point of failure is if it can be helped at all.