If using std::random_device fails, fall back to just time(nullptr)

For instance, if using LibreOfficeKit in a chroot jail, there might
not be a /dev/urandom, which causes the std::random_device ctor to
throw a std::runtime_error exception, at least in the libstdc++ I
have.

Change-Id: Icc91a4ddf92ce66c66b6ffb8b4d1a02ab5f29ee9

comphelper/source/misc/random.cxx

@@ -12,9 +12,11 @@
 
 #include <comphelper/random.hxx>
 #include <rtl/instance.hxx>
+#include <rtl/ustring.hxx>
 #include <assert.h>
 #include <time.h>
 #include <random>
+#include <stdexcept>
 
 // this is nothing but a simple wrapper around
 // the std::random generators
@@ -36,6 +38,8 @@ struct RandomNumberGenerator
 {
     STD_RNG_ALGO global_rng;
     RandomNumberGenerator()
+    {
+        try
         {
             std::random_device rd;
             // initialises the state of the global random number generator
@@ -45,6 +49,12 @@ struct RandomNumberGenerator
             // sequence of numbers, e.g. via myrand.distribution().reset())
             global_rng.seed(rd() ^ time(nullptr));
         }
+        catch (std::runtime_error& e)
+        {
+            SAL_WARN("comphelper.random", OUString("Using std::random_device failed: ") << e.what());
+            global_rng.seed(time(nullptr));
+        }
+    }
 };
 
 class theRandomNumberGenerator : public rtl::Static<RandomNumberGenerator, theRandomNumberGenerator> {};