yara: 3.7.1 -> 3.8.1

This fixes issues CVE-2018-12034 & CVE-2018-12035. They are OOB read &
write issues of the internal VM. Details can be retrieved at [1] & [2].

[1] https://github.com/VirusTotal/yara/issues/891
[2] https://bnbdr.github.io/posts/swisscheese/

pkgs/tools/security/yara/default.nix

@@ -5,34 +5,16 @@
 }:
 
 stdenv.mkDerivation rec {
-  version = "3.7.1";
+  version = "3.8.1";
   name = "yara-${version}";
 
   src = fetchFromGitHub {
     owner = "VirusTotal";
     repo = "yara";
     rev = "v${version}";
-    sha256 = "05smkn4ii8irx6ccnzrhwa39pkmrjyxjmfrwh6mhdd8iz51v5cgz";
+    sha256 = "1ys2y5f2cif3g42daq646jcrn2na19zkx7fds2gnavj5c1rk7463";
   };
 
-  # FIXME: this is probably not the right way to make it work
-  # make[2]: *** No rule to make target 'libyara/.libs/libyara.a', needed by 'yara'.  Stop.
-  prePatch = ''
-    cat >staticlibrary.patch <<EOF
-    --- a/Makefile.am 2015-11-01 11:39:12.000000000 +0100
-    +++ b/Makefile.am 2015-11-01 11:45:32.000000000 +0100
-    @@ -12 +12 @@
-    -yara_LDADD = libyara/.libs/libyara.a
-    +yara_LDADD = libyara/.libs/libyara${stdenv.hostPlatform.extensions.sharedLibrary}
-    @@ -15 +15 @@
-    -yarac_LDADD = libyara/.libs/libyara.a
-    +yarac_LDADD = libyara/.libs/libyara${stdenv.hostPlatform.extensions.sharedLibrary}
-    EOF
-  '';
-  patches = [
-    "staticlibrary.patch"
-  ];
-
   buildInputs = [ autoconf automake libtool pcre]
     ++ stdenv.lib.optionals withCrypto [ openssl ]
     ++ stdenv.lib.optionals enableMagic [ file ]