linux module handling: support kernels without modules

pkgs/build-support/kernel/modules-closure.sh

@@ -1,5 +1,19 @@
 source $stdenv/setup
 
+# When no modules are built, the $out/lib/modules directory will not
+# exist. Because the rest of the script assumes it does exist, we
+# handle this special case first.
+if ! test -d "$out/lib/modules"; then
+    if test -z "$rootModules" || test -n "$allowMissing"; then
+        mkdir -p "$out"
+        exit 0
+    else
+        echo "Required modules: $rootModules"
+        echo "Can not derive a closure of kernel modules because no modules were provided."
+        exit 1
+    fi
+fi
+
 version=$(cd $kernel/lib/modules && ls -d *)
 
 echo "kernel version is $version"

pkgs/os-specific/linux/kmod/aggregator.nix

@@ -9,6 +9,12 @@ buildEnv {
     ''
       source ${stdenv}/setup
 
+      if ! test -d "$out/lib/modules"; then
+        echo "No modules found."
+        # To support a kernel without modules
+        exit 0
+      fi
+
       kernelVersion=$(cd $out/lib/modules && ls -d *)
       if test "$(echo $kernelVersion | wc -w)" != 1; then
          echo "inconsistent kernel versions: $kernelVersion"