Avoid creating empty .so/.dylib/.dll files

[MrElendig]

Compiling rust 0.5 ends up with these .so files being empty:
librusti.so
librustdoc.so
libcargo.so
librustc.so

Compilers/tools:
gcc: 4.7.2
llvm: 3.2
libffi 3.0.11

Compilation output etc:
https://gist.github.com/4524662

[catamorphism]

This is harmless (the empty .so files just get used to track dependencies in the build system). But, I agree that the error messages you're seeing from ldconfig are confusing. We should fix this; @brson suggested using a meaningless extension for the empty files, so that we can still use them for dependencies but ldconfig won't complain about them.

I'll change the title to reflect the proposed fix.

[brson]

#5217 is related

[thestinger]

Is it possible to replace these with symlinks?

[thestinger]

Fixed by 2cbfe6d.