Error: ‘F_GETFD’ undeclared when trying to compile for host tests on linux in espidf

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/home/vscode/esp/esp-idf/components/esp_http_server/src/httpd_sess.c: In function ‘fd_is_valid’:
/home/vscode/esp/esp-idf/components/esp_http_server/src/httpd_sess.c:60:22: error: ‘F_GETFD’ undeclared (first use in this function); did you mean ‘F_GETFL’?
   60 |     return fcntl(fd, F_GETFD) != -1 || errno != EBADF;
      |                      ^~~~~~~
      |                      F_GETFL
/home/vscode/esp/esp-idf/components/esp_http_server/src/httpd_sess.c:60:22: note: each undeclared identifier is reported only once for each function it appears in
/home/vscode/esp/esp-idf/components/esp_http_server/src/httpd_sess.c:61:1: error: control reaches end of non-void function [-Werror=return-type]
   61 | }
      | ^
cc1: some warnings being treated as errors
[5/184] Linking C static library esp-idf/nvs_flash/libnvs_flash.a
ninja: build stopped: subcommand failed.
ninja failed with exit code 1, output of the command is in the /workspace/build/log/idf_py_stderr_output_38441 and /workspace/build/log/idf_py_stdout_output_38441
vscode@198e7f08a570:/workspace$

not much more to say, really, trying to compile my project for set-target to linux and getting the above…after looking around I have set sdkconfig.defaults.linux to contain CONFIG_FREERTOS_NUMBER_OF_CORES=1. At a bit of a loss on this one.

Any help would be gratefully and greatly appreciated