journald: fix source file location

This is what my manpage says, and what the original blog post [1] says
as well.

Also, `sd_journal_send` can add the location of its own invocation to
the log. That's typically not what we want, so we have to suppress that
feature and instead put whatever is inside the spdlog message into the
journal.

[1] http://0pointer.de/blog/projects/journal-submit.html

include/spdlog/sinks/systemd_sink.h

@@ -8,6 +8,9 @@
 #include "spdlog/details/synchronous_factory.h"
 
 #include <array>
+#ifndef SD_JOURNAL_SUPPRESS_LOCATION
+#define SD_JOURNAL_SUPPRESS_LOCATION
+#endif
 #include <systemd/sd-journal.h>
 
 namespace spdlog {
@@ -63,7 +66,7 @@ protected:
         else
         {
             err = (sd_journal_send)("MESSAGE=%.*s", static_cast<int>(length), msg.payload.data(), "PRIORITY=%d", syslog_level(msg.level),
-                "SOURCE_FILE=%s", msg.source.filename, "SOURCE_LINE=%d", msg.source.line, "SOURCE_FUNC=%s", msg.source.funcname, nullptr);
+                "CODE_FILE=%s", msg.source.filename, "CODE_LINE=%d", msg.source.line, "CODE_FUNC=%s", msg.source.funcname, nullptr);
         }
 
         if (err)