beamPackages.buildMix: fix install hooks not running (#530508)

pkgs/development/beam-modules/hooks/beam-module-install-hook.sh

@@ -7,6 +7,8 @@
 beamModuleInstallHook() {
   echo "Executing beamModuleInstallHook"
 
+  runHook preInstall
+
   mkdir -p "$out/lib/erlang/lib/${beamModuleName}-${version}"
 
   # default to rebar3
@@ -25,6 +27,8 @@ beamModuleInstallHook() {
     fi
   done
 
+  runHook postInstall
+
   echo "Finished beamModuleInstallHook"
 }