Support custom eol style using a define in tweakme.h

By default use the platform convention (i.e. "\r\n" on windows), but
make it possible to set a custom end-of-line string without implementing
a custom formatter.

include/spdlog/details/pattern_formatter_impl.h

@@ -619,7 +619,11 @@ inline void spdlog::pattern_formatter::format(details::log_msg& msg)
             f->format(msg, tm_time);
         }
         //write eol
+#if defined(SPDLOG_EOL)
+        msg.formatted << SPDLOG_EOL;
+#else
         msg.formatted << details::os::eol();
+#endif
     }
     catch(const fmt::FormatError& e)
     {

include/spdlog/tweakme.h

@@ -63,3 +63,8 @@
 // Uncomment to enable usage of wchar_t for file names on Windows.
 // #define SPDLOG_WCHAR_FILENAMES
 ///////////////////////////////////////////////////////////////////////////////
+
+///////////////////////////////////////////////////////////////////////////////
+// uncomment the below to override spdlog's default eol
+// #define SPDLOG_EOL "\n"
+///////////////////////////////////////////////////////////////////////////////