Turns out the reason GCC wasn't as smart about startup code for
shared objects as we hoped is because nobody told it to be :D
Change the STARTFILE_SPEC and ENDFILE_SPEC in gcc/config/serenity.h to
skip crt0.o and to link the S variants of crtbegin
and crtend for shared objects.
Because we're using the crtbegin and crtend from libgcc, also tell
libgcc in libgcc/config.host to compile crtbeginS and crtendS from
crtstuff.c.
When running ./package.sh to rebuild an already installed port, we would not
want to spend time re-downlodaing the same tarball again. Ideally, this should
use some sort of hash checking to ensure the file is not truncated or something,
but this is good enough for now.
Ports/.port_include.sh, Toolchain/BuildIt.sh, Toolchain/UseIt.sh
have been left largely untouched due to use of Bash-exclusive
functions and variables such as $BASH_SOURCE, pushd and popd.
Much redundancy is removed from package scripts with this system.
It also supports simple dependency management, uninstalling (through
BSD ports style plist files), cleaning up after itself (with clean,
clean_dist, clean_all commands), etc.
