First trouble is incorrect qpdf buiding. Qpdf is mandatory dependence of cups. In current master, qpdf builds with incorrect --no-random option. On any work< qpdf send 'no such file' error. For example: qpdf /usr/share/cups/data/secret.pdf - This commmand must get PDF file in stdout.But only 'No such file or directory' error present. 0/1 patch fix this by changing configure options to with-random=/dev/random. Next global problem - cups-filters need ghostscript. >From https://github.com/OpenPrinting/cups-filters/blob/master/README : By default, pdftops uses Ghostscript if this does not get changed at compile time, for example by the Linux distribution vendor. 0/2 patch fix id by settinbg ghostscript as default render if ghostscript enabled in voard config. Last trouble - ghostscript building without cups support. 0/3 patch fix is by removing disable-patch option. Now, if cups is enabled, it will be added to dependencies and correct configure options added to ghostscript building. Also fixed ghostscript buildroot building issue with unpleasant hack in configure.ac, which broke pkg-config. It's broke cups search by ghostscript configure script. GHOSTSCRIPT_CUPS_CONFIG_FIX also needed for this task.
I think this issue can be set as fixed since the 3 patches have been merged: - https://git.buildroot.net/buildroot/commit?id=69dfbbd33b2afab0814c5674b0bc7f5464941fbc - https://git.buildroot.net/buildroot/commit?id=59acde11f9f93e99df309b2ed7a14795bedbcfa9 - https://git.buildroot.net/buildroot/commit?id=f9e359d7653f4af32a491e2baf4b6e524554174b
Issue fixed. Thanks!