coreboot: add postCommands

coreboot.nix

@@ -4,10 +4,11 @@
 , gnat, bison, flex, zlib, python3
 , libfaketime, gnumake
 # options
-, rev           # coreboot git revision
-, sources       # coreboot sources attrset
-, arch ? "i386" # target architecture
-, conf ? { }    # coreboot configuration
+, rev               # coreboot git revision
+, sources           # coreboot sources attrset
+, arch ? "i386"     # target architecture
+, conf ? { }        # coreboot configuration
+, postCommands ? "" # command to run after build
 }:
 
 let
@@ -132,6 +133,8 @@ in rec {
         "XGCCPATH=${toolchain}/bin/"
       ];
 
+    postBuild = postCommands;
+
     installPhase = ''
       install -Dm644 build/coreboot.rom $out/coreboot.rom
       install -Dm644 .config $out/config