gcc474: cosmetics - one option per line
gcc474: enable installation of libssp

this installs
libssp_nonshared.a
libssp.a
libssp.so*
into lib/.

the latter ones are probably unwanted, since musl already supplies the
regular libssp functionality. they will be removed in another commit.

libssp_nonshared.a is required for binaries compiled with
-fPIE -fstack-protector-all on some architectures, most notably i386,
where GOT lookup of functions requires multiple steps (instructions).
so, as an optimization, in order not to bloat the function prologue/epilogue
of every single stack-protected function unnecessarily,
it was decided to simply emit a jump to a local wrapper function which then
calls the real __stack_chk_fail function via GOT.
that's the reason the function has to be statically linked in and resides
in a separate library.
see ssp-local.c in gcc tree for the functions' code.

this is the first step in getting #274 solved.
gcc474: fix a line that returns error on rebuild (regression from enabling ssp)

gcc474 is one of the crucial packages blacklisted in the butch
build template, which must not be removed prior to rebuilding, since it
would render the system unfunctional.

since we enabled ssp in the previous commit, gcc installs a directory ssp
into its internal include dir in the DESTDIR.
this piece of code here copies the files from that include dir to another
location, in the assumption that they're only regular files.
as ssp is a directory, the cp command now returns error and displays the
message "omitting directory..." after a rebuild.

fixing it by just ignoring the error, as we dont need the ssp dir in the
copy target.
gcc474: use magic flag preventing creation of the lib64 directory on x86_64
gcc474: remove incompatible libssp.* libs

musl already has the libssp functionality built-in, we need only
libssp-nonshared.a.
gcc474: always link against ssp_nonshared when using stack protector

closes #274