Fix cmake build error dirent (#1536)

* Better ignore support for idea projects.

Added a wildcard at the end because different configurations would have a diffeerent build directory.

* Removed external from being a relative include directory for target raylib.

Fixes #1533

src/CMakeLists.txt

@@ -105,7 +105,6 @@ target_include_directories(raylib
                            $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
                            PRIVATE
                            ${CMAKE_CURRENT_SOURCE_DIR}
-                           ${CMAKE_CURRENT_SOURCE_DIR}/external
                            ${CMAKE_BINARY_DIR} # For cmake/config.h
                            ${OPENGL_INCLUDE_DIR}
                            ${OPENAL_INCLUDE_DIR}