add basic types and fix cmake

src/external/CMakeLists.txt

@@ -7,3 +7,16 @@ add_files(
 	toml++/toml.hpp
 	toml++/toml.h
 )
+
+# Expose each external library's own directory on the include path so that
+# source files can reference its headers without a subdirectory prefix:
+#   #include "catch.hpp"      // instead of "catch/catch.hpp"
+#   #include "tinyexpr.h"     // instead of "tinyexpr/tinyexpr.h"
+#   #include "toml.hpp"       // instead of "toml++/toml.hpp"
+set(LIB_INCLUDE_PATH
+	${LIB_INCLUDE_PATH}
+	${CMAKE_CURRENT_SOURCE_DIR}/catch
+	${CMAKE_CURRENT_SOURCE_DIR}/tinyexpr
+	${CMAKE_CURRENT_SOURCE_DIR}/toml++
+	PARENT_SCOPE
+)