BifCl.cmake needs Zeek::BifCl triggered when touching CMakeLists.txt

[awelzel]

When developing a plugin with a ./configure && make workflow, in Zeek 5.2, after modifying/touching CMakeLists.txt (e.g adding more sources or changing flags), then re-running make would trigger a cmake re-run and continue the build usually succeeding. With latest master, modifying the CMakeLists.txt now hard-fails the re-run of cmake:

In a zeek-community-id checkout:

$ ./configure
$ cd build
$ make    # success
$ touch ../CMakeLists.txt
$ make    # success expected

With Zeek 6.0-rc1, the last step fails as follows:

$ make
CMake Error at /opt/zeek-dev/share/zeek/cmake/BifCl.cmake:2 (message):
  BifCl.cmake needs Zeek::BifCl
Call Stack (most recent call first):
  /opt/zeek-dev/share/zeek/cmake/ZeekPlugin.cmake:66 (include)
  CMakeLists.txt:22 (include)


-- Configuring incomplete, errors occurred!
See also "/home/awelzel/corelight-oss/zeek-community-id/build/CMakeFiles/CMakeOutput.log".
See also "/home/awelzel/corelight-oss/zeek-community-id/build/CMakeFiles/CMakeError.log".
make: *** [Makefile:401: cmake_check_build_system] Error 1

The workaround is to remove the build directory and re-run ./configure, but IMO the 5.2.2 behavior was nicer as it just worked. Above error is also not actionable for someone running into it.

@Neverlord - I see there's some caching if bootstrapping ran and that seems to cause the issue:

cmake/ZeekPlugin.cmake

Lines 59 to 64 in 4e41cdd

	# Make sure BifCl and BinPAC are available.
	if (NOT ZEEK_PLUGIN_INTERNAL_BUILD AND NOT ZEEK_PLUGIN_HAD_BOOTSTRAPPING)
	zeek_plugin_bootstrapping()
	# Remember that we have called the function to not call it again.
	set(ZEEK_PLUGIN_HAD_BOOTSTRAPPING ON CACHE BOOL "Plugin bootstrapping has completed." FORCE)
	endif ()

[mmguero]

Please ignore my references to the amzn plugins an hour ago, I was conflating two issues. After some discussion in the slack channel I've been set straight. Thanks!