Remove Lazy

This fixes a crash during startup when compiling Nix as a single
compilation unit.

src/libutil/lazy.hh

@@ -1,48 +0,0 @@
-#include <exception>
-#include <functional>
-#include <mutex>
-
-namespace nix {
-
-/* A helper class for lazily-initialized variables.
-
-     Lazy<T> var([]() { return value; });
-
-   declares a variable of type T that is initialized to 'value' (in a
-   thread-safe way) on first use, that is, when var() is first
-   called. If the initialiser code throws an exception, then all
-   subsequent calls to var() will rethrow that exception. */
-template<typename T>
-class Lazy
-{
-
-    typedef std::function<T()> Init;
-
-    Init init;
-
-    std::once_flag done;
-
-    T value;
-
-    std::exception_ptr ex;
-
-public:
-
-    Lazy(Init init) : init(init)
-    { }
-
-    const T & operator () ()
-    {
-        std::call_once(done, [&]() {
-            try {
-                value = init();
-            } catch (...) {
-                ex = std::current_exception();
-            }
-        });
-        if (ex) std::rethrow_exception(ex);
-        return value;
-    }
-};
-
-}

src/libutil/util.cc

@@ -1,4 +1,3 @@
-#include "lazy.hh"
 #include "util.hh"
 #include "affinity.hh"
 #include "sync.hh"
@@ -522,7 +521,10 @@ std::string getUserName()
 }
 
 
-static Lazy<Path> getHome2([]() {
+Path getHome()
+{
+    static Path homeDir = []()
+    {
         auto homeDir = getEnv("HOME");
         if (!homeDir) {
             std::vector<char> buf(16384);
@@ -534,9 +536,9 @@ static Lazy<Path> getHome2([]() {
             homeDir = pw->pw_dir;
         }
         return *homeDir;
-});
-
-Path getHome() { return getHome2(); }
+    }();
+    return homeDir;
+}
 
 
 Path getCacheDir()