unit_tests: fix build with GCC 5.4.0 on ubuntu

tests/unit_tests/is_hdd.cpp

@@ -6,12 +6,12 @@
 TEST(is_hdd, linux_os_root)
 {
   std::string path = "/";
-  EXPECT_TRUE(tools::is_hdd(path.c_str()));
+  EXPECT_TRUE(tools::is_hdd(path.c_str()) != boost::none);
 }
 #else
 TEST(is_hdd, unknown_os)
 {
   std::string path = "";
-  EXPECT_FALSE(tools::is_hdd(path.c_str()));
+  EXPECT_FALSE(tools::is_hdd(path.c_str()) != boost::none);
 }
 #endif

tests/unit_tests/wipeable_string.cpp

@@ -194,13 +194,13 @@ TEST(wipeable_string, parse_hexstr)
   ASSERT_EQ(boost::none, epee::wipeable_string("0").parse_hexstr());
   ASSERT_EQ(boost::none, epee::wipeable_string("000").parse_hexstr());
 
-  ASSERT_TRUE((s = epee::wipeable_string("").parse_hexstr()));
+  ASSERT_TRUE((s = epee::wipeable_string("").parse_hexstr()) != boost::none);
   ASSERT_EQ(*s, "");
-  ASSERT_TRUE((s = epee::wipeable_string("00").parse_hexstr()));
+  ASSERT_TRUE((s = epee::wipeable_string("00").parse_hexstr()) != boost::none);
   ASSERT_EQ(*s, epee::wipeable_string("", 1));
-  ASSERT_TRUE((s = epee::wipeable_string("41").parse_hexstr()));
+  ASSERT_TRUE((s = epee::wipeable_string("41").parse_hexstr()) != boost::none);
   ASSERT_EQ(*s, epee::wipeable_string("A"));
-  ASSERT_TRUE((s = epee::wipeable_string("414243").parse_hexstr()));
+  ASSERT_TRUE((s = epee::wipeable_string("414243").parse_hexstr()) != boost::none);
   ASSERT_EQ(*s, epee::wipeable_string("ABC"));
 }