kcov: fix build on aarch64

Apparently, without this patch `NT_PRSTATUS` is not found. So the patch
adds the include apparently necessary. `NT_PRSTATUS` is also defined in
`<linux/ptrace.h>`, which would likely have been a better name, were it
not in the `linux/` directory, which is a priori not stable.

The need to do that is kind of weird (the change was introduced in [1],
and fedora apparently didn't need this additional import), but I'll try
to upstream it.

[1] https://github.com/SimonKagstrom/kcov/pull/239

pkgs/development/tools/analysis/kcov/aarch64_nt_prstatus.patch

@@ -0,0 +1,12 @@
+diff --git a/src/engines/ptrace.cc b/src/engines/ptrace.cc
+index 59b615f..e02cddf 100644
+--- a/src/engines/ptrace.cc
++++ b/src/engines/ptrace.cc
+@@ -21,6 +21,7 @@
+ 
+ #if defined(__aarch64__)
+ #  include <sys/uio.h>
++#  include <elf.h>
+ #endif
+ 
+ #include <map>

pkgs/development/tools/analysis/kcov/default.nix

@@ -16,6 +16,8 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ zlib curl elfutils python libiberty libopcodes ];
 
+  patches = [ ./aarch64_nt_prstatus.patch ];
+
   enableParallelBuilding = true;
 
   meta = with stdenv.lib; {