_PKG_CONFIG_LIBS_LIST might be empty

[nim65s]

Hi,

jrl-cmakemodules/Config.cmake.in

Line 17 in dcec7d7

string(FIND ${_PKG_CONFIG_LIBS_LIST} ", " _is_comma_space)

This break hpp-environments, because it generates the following Config:

set(_PACKAGE_CONFIG_LIBRARIES "")
set(_PKG_CONFIG_LIBDIR "/home/nim/local/robotpkg/install/lib")
set(_PKG_CONFIG_LIBS_LIST "")
string(FIND ${_PKG_CONFIG_LIBS_LIST} ", " _is_comma_space)

Which fails in dependent packages with:

CMake Error at …/lib/cmake/hpp-environments/hpp-environmentsConfig.cmake:38 (string):
  string sub-command FIND requires 3 or 4 parameters.
Call Stack (most recent call first):
  cmake/package-config.cmake:80 (find_package)
  CMakeLists.txt:72 (ADD_PROJECT_DEPENDENCY)

[nim65s]

I understand that we need to ensure that what was working before will continue to work for some time.

But I think we are adding a lot of code (I can't count issues & PR on this subject) to patch this, and maybe that would be nice to opt-out of all of this legacy, especially when trying to move on to newer and cleaner practices.

[nim65s]

And actually, with an older CMake version, hpp-environments is not configuring at all:

CMake Error at cmake/package-config.cmake:145 (list):
list sub-command REMOVE_DUPLICATES requires list to be present.