gcc: drop include-fixed/bits/statx.h

At least on armv7l-linux bootstrapTools fixed version of bits/statx.h
breaks the header:
    https://github.com/NixOS/nixpkgs/pull/209870#issuecomment-1501201452

Drop the header along with other already cleaned ones.

pkgs/development/compilers/gcc/builder.sh

@@ -262,7 +262,7 @@ postInstall() {
     fi
 
     # Get rid of some "fixed" header files
-    rm -rfv $out/lib/gcc/*/*/include-fixed/{root,linux,sys/mount.h}
+    rm -rfv $out/lib/gcc/*/*/include-fixed/{root,linux,sys/mount.h,bits/statx.h}
 
     # Replace hard links for i686-pc-linux-gnu-gcc etc. with symlinks.
     for i in $out/bin/*-gcc*; do