Could not find pkg-config information for ignition-tools

[chapulina]

When doing a ign_find_package(ignition-tools REQUIRED) call, we get:

CMake Warning (dev) at /home/chapulina/blueprint_ws/install/share/cmake/ignition-cmake2/cmake2/IgnUtils.cmake:378 (message):
   -- THIS MESSAGE IS INTENDED FOR IGNITION-LAUNCH AUTHORS --
      (IF YOU SEE THIS, PLEASE REPORT IT)
                                                                      
  Could not find pkg-config information for ignition-tools.  It was not      
  provided by the find-module for the package, nor was it explicitly passed
  into the call to ign_find_package(~).  This is most likely an error in this                                                     
  project's use of ign-cmake.                                                         
Call Stack (most recent call first):                                                                                       
  CMakeLists.txt:50 (ign_find_package)                                                                     
This warning is for project developers.  Use -Wno-dev to suppress it.

Note that this warning is not shown if finding QUIETly.

[chapulina]

This workaround solves the issue:

ign_find_package(ignition-tools
  REQUIRED
  PKGCONFIG "ignition-tools")

See for example gazebosim/gz-launch#44