cmake: produce civetweb.h, again

[mattbenjamin]

The recent change to do this logic with file copy (and in src/rgw)
resolved the build problem, but now updates to the civetweb
submodule were not reflected in the build.

Move the copy into a custom target which will always source the
current submodule version at build time.

Signed-off-by: Matt Benjamin mbenjamin@redhat.com

[yehudasa]

lgtm, also tested

[ghost]

https://jenkins.ceph.com/job/ceph-pull-requests/14144/console

[  0%] Building CXX object src/CMakeFiles/common_texttable_obj.dir/common/TextTable.cc.o
CMake Error: cmake version 2.8.12.2
Usage: /usr/bin/cmake -E [command] [arguments ...]
Available commands: 
  chdir dir cmd [args]...   - run command in a given directory
  compare_files file1 file2 - check if file1 is same as file2
  copy file destination     - copy file to destination (either file or directory)
  copy_directory source destination   - copy directory 'source' content to directory 'destination'
  copy_if_different in-file out-file  - copy file if input has changed
  echo [string]...          - displays arguments as text
  echo_append [string]...   - displays arguments as text but no new line
  environment               - display the current environment
  make_directory dir        - create a directory
  md5sum file1 [...]        - compute md5sum of files
  remove [-f] file1 file2 ... - remove the file(s), use -f to force it
  remove_directory dir      - remove a directory and its contents
  rename oldname newname    - rename a file or directory (on one volume)
  tar [cxt][vfz][cvfj] file.tar [file/dir1 file/dir2 ...]
                            - create or extract a tar or zip archive
  time command [args] ...   - run command and return elapsed time
  touch file                - touch a file.
  touch_nocreate file       - touch a file but do not create it.
Available on UNIX only:
  create_symlink old new    - create a symbolic link new -> old
make[3]: *** [src/rgw/CMakeFiles/civetweb_h] Error 1
make[2]: *** [src/rgw/CMakeFiles/civetweb_h.dir/all] Error 2

[mattbenjamin]

(The jenkins report shows cmake w/the required commands, something wrong with quoting or formatting, or else the source file was not present [submodule]; will try to run it down)

[cbodley]

testing this, i see that it forces a rebuild/link of radosgw every time you make, even if the civetweb.h is unchanged

you might be able to use cmake -E copy_if_different ... to work around this - otherwise i think add_custom_command() is what you want

[mattbenjamin]

@cbodley yeah, copy_if_different is more correct; I really prefer the target machinery, it's too bad cmake is (still?) slightly goofy in this area

[mattbenjamin]

@yehudasa this should build on centos 7 now; I had tried to be clever and use the BYPRODUCTS option to make_custom_target--which most of our supported cmakes don't understand.

[yehudasa]

@mattbenjamin lgtm, but I'm not sure I'm qualified to review this one

[mattbenjamin]

@yehudasa This version built as expected, so whether it merges is I guess down to whether we want to resolve the problem of tracking civetweb submodule version.

[cbodley]

retested and it works for me 👍