Description of problem:

When libjpeg-turbo-devel is installed, a CMake configuration is placed in /usr/lib64/cmake/libjpeg-turbo that contains the target definitions for both libjpeg-turbo::jpeg and libjpeg-turbo::turbojpeg. However, turbojpeg[-devel] is a separate package that may or may not be installed on the system.

Version-Release number of selected component (if applicable):

libjpeg-turbo-2.1.0-3.fc35

How reproducible:
100%

Steps to Reproduce:

1. sudo dnf install libjpeg-turbo-devel

2. sudo dnf remove turbojpeg-devel  # Just to  be sure

3. Create two files:

tjtest.cpp
==========
#include <cassert>
#include <turbojpeg.h>
int main() {
	auto cmp = tjInitCompress();
	assert(cmp != nullptr && "Didn't get handle!");
}	

CMakeLists.txt
==============
cmake_minimum_required(VERSION 3.10)
project(tjtest VERSION 0.1 LANGUAGES CXX)
find_package(libjpeg-turbo REQUIRED)
add_executable(tjtest tjtest.cpp)
target_link_libraries(tjtest PUBLIC libjpeg-turbo::turbojpeg)


4. Attempt to build the tjtest program:

   cmake -B build -S .
   cmake --build build


Actual results:

$ cmake -B build -S .
-- The CXX compiler identification is GNU 11.2.1
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/lib64/ccache/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /var/tmp/build

$ cmake --build build
[ 50%] Building CXX object CMakeFiles/tjtest.dir/tjtest.cpp.o
/var/tmp/tjtest.cpp:2:10: fatal error: turbojpeg.h: No such file or directory
    2 | #include <turbojpeg.h>
      |          ^~~~~~~~~~~~~
compilation terminated.
gmake[2]: *** [CMakeFiles/tjtest.dir/build.make:76: CMakeFiles/tjtest.dir/tjtest.cpp.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/tjtest.dir/all] Error 2
gmake: *** [Makefile:91: all] Error 2


Expected results:

CMake fails to find the turbojpeg package dependency due to turbojpeg-devel not being installed, and errors out without configuring the build environment.

(Or, turbojpeg-devel is combined into libjpeg-turbo-devel instead of being a separate package, since it already includes the configuration.)