linux-testing: Fix arg list too long in modinst

With the default kernel and thus with the build I have tested in
74ec94bfa2, we get an error during
modules_install:

make[2]: execvp: /nix/store/.../bin/bash: Argument list too long

I haven't noticed this build until I actually tried booting using this
kernel because make didn't fail here.

The reason this happens within Nix and probably didn't yet surface in
other distros is that programs only have a limited amount of memory
available for storing the environment and the arguments.

Environment variables however are quite common on Nix and thus we
stumble on problems like this way earlier - in this case Linux 4.8 - but
I have noticed this in 4.7-next as well already.

The fix is far from perfect and suffers performance overhead because we
now run grep for every *.mod file instead of passing all *.mod files
into one single invocation of grep.

But comparing the performance overhead (around 1s on my machine) with
the overall build time of the kernel I think the overhead really is
neglicible.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

pkgs/os-specific/linux/kernel/patches.nix

@@ -74,6 +74,11 @@ rec {
       patch = ./mips-ext3-n32.patch;
     };
 
+  modinst_arg_list_too_long =
+    { name = "modinst-arglist-too-long";
+      patch = ./modinst-arg-list-too-long.patch;
+    };
+
   ubuntu_fan_4_4 =
     { name = "ubuntu-fan";
       patch = ./ubuntu-fan-4.4.patch;