Use relative includes and create spdlog_config.h

cmake/spdlog_config.h.in

@@ -0,0 +1,35 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+
+// Auto generated file with compile time flags with which spdlog was compiled
+// DO NOT EDIT MANUALLY
+
+#pragma once
+
+// Support wchar filenames (Windows only)
+#cmakedefine SPDLOG_WCHAR_FILENAMES
+
+#cmakedefine SPDLOG_NO_EXCEPTIONS
+
+// Use CLOCK_REALTIME_COARSE on Linux
+#cmakedefine SPDLOG_CLOCK_COARSE
+
+// Prevent child processes from inheriting log file descriptors
+#cmakedefine SPDLOG_PREVENT_CHILD_FD
+
+// Prevent spdlog from querying the thread id on each log call
+#cmakedefine SPDLOG_NO_THREAD_ID
+
+// Prevent spdlog from using std::atomic for log levels
+#cmakedefine SPDLOG_NO_ATOMIC_LEVELS
+
+// Disable default logger creation
+#cmakedefine SPDLOG_DISABLE_DEFAULT_LOGGER
+
+// Use std::format instead of fmtlib
+#cmakedefine SPDLOG_USE_STD_FORMAT
+
+// Use external fmtlib instead of bundled
+#cmakedefine SPDLOG_FMT_EXTERNAL
+