Removes content nothing between minimal-bootstrap and stage 4 ever uses: glibc share/i18n + lib/gconv (localedef and iconv() against the bootstrap glibc are never invoked downstream); python lib-dynload/{_decimal,_socket,_asyncio,_hashlib,_blake2,_sha*,_md5,_hmac,CJK codecs,_zoneinfo,_lsprof,syslog} plus idlelib/tkinter/turtle*/ensurepip (glibc's build-time scripts only use os/re/subprocess/argparse/pathlib/collections); binutils bin/{gprof,addr2line,elfedit}; share/{info,man} and gcc share/gcc-*/python (libstdc++ gdb pretty-printers).

Self-size: 940 MB -> ~870 MB. Largest contributors: glibc -38 MB, python -15 MB, binutils -7 MB.

Adds --enable-checking=release and --disable-{libgomp,libquadmath,libitm,libvtv,libssp,libatomic,libstdcxx-pch,nls} to all GCCs (those runtime libs are unused by the stdenv); switches gcc-4.6{,cxx} to install-strip; adds --disable-nls to binutils and coreutils; adds --disable-test-modules --without-ensurepip --without-static-libpython to python.

Bootstrap self-size 1.45 GB -> 940 MB; gcc46-cxx -14%, glibc -10%, gcc-latest -6% wall on the heavy builds.

(make -j was tried on tcc-built derivations and broke them silently; NOTE comments left in the affected files so this isn't re-attempted.)