Enable PIC for static library on UNIX systems

Added an `endif()` statement to close the `if(WIN32)` block.
Introduced a new `if(UNIX)` block to set `POSITION_INDEPENDENT_CODE`
to `ON` for the `lib` target. This ensures the static library is
compiled with Position Independent Code on UNIX systems, which is
necessary for creating shared libraries.

lib/CMakeLists.txt

@@ -88,4 +88,8 @@ target_include_directories(lib PRIVATE  ${CMAKE_CURRENT_BINARY_DIR})  # this is
 
 if(WIN32)
  target_compile_definitions(lib PRIVATE _WIN32API=1)
+endif()
+if(UNIX)
+  # Enable PIC for the static library
+	set_target_properties(lib PROPERTIES POSITION_INDEPENDENT_CODE ON)
 endif()