[Lib/Derivations] init with isBroken helper

Returns true if the parameter is not a derivation or if trying to
evaluate the derivation would fail.

lib/default.nix

@@ -12,5 +12,6 @@ let
     attrsets = callLibs ./attrsets.nix;
     types = callLibs ./types.nix;
     debug = callLibs ./debug.nix;
+    derivations = callLibs ./derivations.nix;
   });
 in myLib

lib/derivations.nix

@@ -0,0 +1,15 @@
+{lib, myLib, ...}:
+with lib;
+rec {
+  isBroken = x:
+    let
+      tryX = builtins.tryEval x;
+    in
+      if
+        tryX.success && (isDerivation tryX.value)
+      then
+        tryX.value.meta.insecure || tryX.value.meta.broken
+      else   
+        true
+    ;
+}