linux stdenv: Avoid assert false

On one hand, don't want to pass garbage that affects hash, on the other
hand footguns are bad.

Now, factored out the derivation so only need to pass in what is used.

pkgs/stdenv/linux/bootstrap-tools/scripts/unpack-bootstrap-tools.sh

@@ -0,0 +1,63 @@
+# Unpack the bootstrap tools tarball.
+echo Unpacking the bootstrap tools...
+$builder mkdir $out
+< $tarball $builder unxz | $builder tar x -C $out
+
+# Set the ELF interpreter / RPATH in the bootstrap binaries.
+echo Patching the bootstrap tools...
+
+if test -f $out/lib/ld.so.?; then
+   # MIPS case
+   LD_BINARY=$out/lib/ld.so.?
+else
+   # i686, x86_64 and armv5tel
+   LD_BINARY=$out/lib/ld-*so.?
+fi
+
+# On x86_64, ld-linux-x86-64.so.2 barfs on patchelf'ed programs.  So
+# use a copy of patchelf.
+LD_LIBRARY_PATH=$out/lib $LD_BINARY $out/bin/cp $out/bin/patchelf .
+
+for i in $out/bin/* $out/libexec/gcc/*/*/*; do
+    if [ -L "$i" ]; then continue; fi
+    if [ -z "${i##*/liblto*}" ]; then continue; fi
+    echo patching "$i"
+    LD_LIBRARY_PATH=$out/lib $LD_BINARY \
+        ./patchelf --set-interpreter $LD_BINARY --set-rpath $out/lib --force-rpath "$i"
+done
+
+for i in $out/lib/librt-*.so $out/lib/libpcre*; do
+    if [ -L "$i" ]; then continue; fi
+    echo patching "$i"
+    $out/bin/patchelf --set-rpath $out/lib --force-rpath "$i"
+done
+
+# Fix the libc linker script.
+export PATH=$out/bin
+cat $out/lib/libc.so | sed "s|/nix/store/e*-[^/]*/|$out/|g" > $out/lib/libc.so.tmp
+mv $out/lib/libc.so.tmp $out/lib/libc.so
+cat $out/lib/libpthread.so | sed "s|/nix/store/e*-[^/]*/|$out/|g" > $out/lib/libpthread.so.tmp
+mv $out/lib/libpthread.so.tmp $out/lib/libpthread.so
+
+# Provide some additional symlinks.
+ln -s bash $out/bin/sh
+ln -s bzip2 $out/bin/bunzip2
+
+# Provide a gunzip script.
+cat > $out/bin/gunzip <<EOF
+#!$out/bin/sh
+exec $out/bin/gzip -d "\$@"
+EOF
+chmod +x $out/bin/gunzip
+
+# Provide fgrep/egrep.
+echo "#! $out/bin/sh" > $out/bin/egrep
+echo "exec $out/bin/grep -E \"\$@\"" >> $out/bin/egrep
+echo "#! $out/bin/sh" > $out/bin/fgrep
+echo "exec $out/bin/grep -F \"\$@\"" >> $out/bin/fgrep
+
+# Provide xz (actually only xz -d will work).
+echo "#! $out/bin/sh" > $out/bin/xz
+echo "exec $builder unxz \"\$@\"" >> $out/bin/xz
+
+chmod +x $out/bin/egrep $out/bin/fgrep $out/bin/xz