Add logging to internal error

Internal error call sites are propagated through the code, and might be
triggered multiple times in the course of a request, which makes them
difficult to track the source of.

This commit changes the internalError() method to include a print of
which invocation within bmcweb triggered the error, using c++20s
std::source_location mechanism.

Note:
clang-13 still doesn't implement std::source_location, so this commit
pulls source_location.hpp from lg2 to be able to support all compilers.

Tested:
Loaded in qemu, and added an internalError() call into systems.hpp for
the /redfish/v1/Systems handler.  Observed that
[CRITICAL "error_messages.cpp":234] Internal Error
../../../../../../workspace/sources/bmcweb/redfish-core/include/../lib/systems.hpp(2820:40)
`redfish::requestRoutesSystemsCollection(App&)::<lambda(const
crow::Request&, const std::shared_ptr<bmcweb::AsyncResp>&)>`:

Got printed to the bmcweb logs.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ic1b4240422445357bc87404de814ad14f86b9edf
diff --git a/include/source_location.hpp b/include/source_location.hpp
new file mode 100644
index 0000000..9880752
--- /dev/null
+++ b/include/source_location.hpp
@@ -0,0 +1,27 @@
+#pragma once
+
+// As of clang-12, clang still doesn't support std::source_location, which
+// means that clang-tidy also doesn't support std::source_location.
+// Inside the libstdc++ implementation of <source_location> is this check of
+// __builtin_source_location to determine if the compiler supports the
+// necessary bits for std::source_location, and if not the header ends up doing
+// nothing.  Use this same builtin-check to detect when we're running under
+// an "older" clang and fallback to std::experimental::source_location instead.
+
+#if __has_builtin(__builtin_source_location)
+#include <source_location>
+
+namespace bmcweb
+{
+using source_location = std::source_location;
+}
+
+#else
+#include <experimental/source_location>
+
+namespace bmcweb
+{
+using source_location = std::experimental::source_location;
+}
+
+#endif