mass rewrite of find parameters to cross-platform style

Fixes #9044, close #9667. Thanks to @taku0 for suggesting this solution.
Now we have no modes starting with `/` or `+`.

Rewrite the `-perm` parameters of find:
 - completely safe: rewrite `/0100` and `+100` to `-0100`,
 - slightly semantics-changing: rewrite `+111` to `-0100`.
I cross-verified the `find` manual pages for Linux, Darwin, FreeBSD.

pkgs/development/libraries/wtk/builder.sh

@@ -21,7 +21,7 @@ rpath=
 for i in $libraries; do
     rpath=$rpath${rpath:+:}$i/lib
 done
-find $out -type f -perm +100 \
+find $out -type f -perm -0100 \
     -exec patchelf --interpreter "$(cat $NIX_CC/nix-support/dynamic-linker)" {} \;
-find $out -type f -perm +100 \
+find $out -type f -perm -0100 \
     -exec patchelf --set-rpath "$rpath" {} \;