Improving library detection in has_lib.sh

[pb82]

Since there seem to be some issues with the current implementation of 'has_lib.sh' why not let the compiler take care of the library search path?

By executing

echo "int main(){return 0;}" | cc -xc -l$1 -o /dev/null -

and checking the return code one could determine the existence of a library. Works with gcc and clang.

Are there problems that i'm missing or could this be a viable solution?