Let build-package.sh setup the $PREFIX/lib/libstdc++.so symlink
before building any package, to make sure that all C++ applications
link against a fully featured C++ standard library.
Avoid explicitly declaring a dependency on the libgnustl package
since everyone may link against it at will and instead mark it as
essential.
- Use version from git, current release has problems with ARM
- Replace rindex with strrchr using C preprocessor
- Don't exit on ltelf_destroy on library that failed to load