icu: refactor to avoid runtime dependency on bash

Bash was considered a runtime dependency as the two files `install-sh`
and `mkinstalldirs` was included in the library output. These files has a shebang
for `#!/bin/sh` which is replaced by nix to point to bash in the fixup phase.

nixos/doc/manual/release-notes/rl-2405.section.md

@@ -439,6 +439,8 @@ The pre-existing [services.ankisyncd](#opt-services.ankisyncd.enable) has been m
 
 - The `erlang-ls` package no longer ships the `els_dap` binary as of v0.51.0.
 
+- `icu` no longer includes `install-sh` and `mkinstalldirs` in the shared folder.
+
 ## Other Notable Changes {#sec-release-24.05-notable-changes}
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->

pkgs/development/libraries/icu/make-icu.nix

@@ -75,6 +75,8 @@ let
         { from = "\${pkglibdir}/pkgdata.inc"; to = "${placeholder "dev"}/lib/icu/pkgdata.inc"; } # --incpkgdatafile
       ];
     in ''
+      rm $out/share/icu/${version}/install-sh $out/share/icu/${version}/mkinstalldirs # Avoid having a runtime dependency on bash
+
       substituteInPlace "$dev/bin/icu-config" \
         ${lib.concatMapStringsSep " " (r: "--replace '${r.from}' '${r.to}'") replacements}
     '');