package.nix: factor out checkInputs

Change-Id: I9fd0fe7f5a6bafbabcef504e186705a94544fdeb

flake.nix

@@ -180,10 +180,7 @@
 
         buildDeps = calledPackage.buildInputs;
 
-        checkDeps = [
-          gtest
-          rapidcheck
-        ];
+        checkDeps = calledPackage.finalAttrs.checkInputs;
 
         internalApiDocsDeps = [
           buildPackages.doxygen

package.nix

@@ -14,6 +14,7 @@
   fileset,
   flex,
   git,
+  gtest,
   jq,
   libarchive,
   libcpuid,
@@ -25,6 +26,7 @@
   mercurial,
   openssl,
   pkg-config,
+  rapidcheck,
   sqlite,
   util-linuxMinimal,
   xz,
@@ -112,4 +114,13 @@ in stdenv.mkDerivation (finalAttrs: {
   ]
     ++ lib.optionals stdenv.isLinux [ libseccomp ]
     ++ lib.optional stdenv.hostPlatform.isx86_64 libcpuid;
+
+  checkInputs = [
+    gtest
+    rapidcheck
+  ];
+
+  # FIXME: Used to make checkInputs accessible from outside the derivation args
+  # during the refactor.
+  passthru.finalAttrs = finalAttrs;
 })