for now, copy bootstrap-tools instead of modify in-place

pkgs/stdenv/linux/bootstrap-tools-musl/default.nix

@@ -0,0 +1,18 @@
+{ system, bootstrapFiles }:
+
+derivation {
+  name = "bootstrap-tools";
+
+  builder = bootstrapFiles.busybox;
+
+  args = [ "ash" "-e" ./scripts/unpack-bootstrap-tools.sh ];
+
+  tarball = bootstrapFiles.bootstrapTools;
+
+  inherit system;
+
+  # Needed by the GCC wrapper.
+  langC = true;
+  langCC = true;
+  isGNU = true;
+}

pkgs/stdenv/linux/bootstrap-tools-musl/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