platform/kevin/fit: add missing pre/postBuild hooks

src/platform/kevin/fit/default.nix

@@ -15,11 +15,13 @@ in stdenv.mkDerivation {
   dontUnpack = true;
   nativeBuildInputs = [ dtc ubootTools ];
   buildPhase = ''
+    runHook preBuild
     mkdir -p $out
     mkimage \
       -D "-I dts -O dtb -p 2048 -W no-unit_address_vs_reg" \
       -f $dtsPath \
       $out/Image.fit
+    runHook postBuild
     '';
   dontInstall = true;
   passAsFile = [ "dts" ];