Custom path for my libraries for find_library - cmake

Question

I am trying to compile openimageio(oiio) on Linux but it's a mess since I know almost nothing about cmake. I don't want and I can't install them on my computer directly in the /usr/local/ directory and that's the problem. I successfully compiled dependencies by executing these bash commands in each library directory :
export workingdir=<path_to_my_project>
./configure --prefix=$workingdir/sdks/deploy
make install
And this works fine, my headers are in a include directory and my libraries are in a lib directory.
Here is the structure of my project :
../<path_to_my_project>
/sdks
/build
/oiio
/png # Successfully compiled
/jpeg # Successfully compiled
/zlib # Successfully compiled
/boost # Successfully compiled
/ilmbase # Successfully compiled
/openexr # Successfully compiled
/deploy
/lib # all .a, .la and .so of successfully compiled libraries
/include # all headers of successfully compiled libraries
The problem is that there is no ./configure available in the oiio library directory so I don't know how to set the prefix path, when I execute the make command, I have errors like this :
CMake Error at /usr/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:108 (message):
Could NOT find PNG (missing: PNG_LIBRARY) (found version "1.6.21")
Call Stack (most recent call first):
/usr/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:315 (_FPHSA_FAILURE_MESSAGE)
/usr/share/cmake/Modules/FindPNG.cmake:105 (find_package_handle_standard_args)
src/libOpenImageIO/CMakeLists.txt:120 (find_package)
So I set variables and it makes no errors but this is not clean and I'm not sure that my libraries are correctly referenced (If I mes up the variable content, it is still working...).
set (PNG_PNG_INCLUDE_DIR "<workingdir>/sdks/deploy/include/libpng16")
set (PNG_LIBRARY_DIR "<workingdir>/sdks/deploy/lib")
Then I tried to create my own FindXXX.cmake files but some don't have a Root variable for the library so anyway I'm not sure if it correctly found the needed files, moreover, it makes errors :
CMake Error at src/cmake/modules/FindPNG.cmake:104 (include):
include could not find load file:
<workingdir>/sdks/build/oiio/src/cmake/modules/FindPackageHandleStandardArgs.cmake
Call Stack (most recent call first):
src/libOpenImageIO/CMakeLists.txt:120 (find_package)
But it finds the cmake file it anyway since other errors are correctly referenced to my file and if I print something in the cmake file it shows up when I run the make command.
Up to know, the command I am running in the oiio directory is make but I would like something that tells to the find_library function to looks other where. I could recall the function with other parameters but I can't use my own FindXXX.cmake files.
In the oiio repository, in the INSTALL file, paragraph line 43, it says to set environment variable for custom libraries, like PNGDIR, but should it point to the deploys directory or the build directory ? And they say to see CMake configuration output, maybe to know what environment variables to set, but I don't know what file they are talking.
I tried so set PNGDIR but it doesn't work, how to know if the variable name should be PNGDIR ? It can also be PNGROOT ?
export PNGDIR=<workingdir>/sdks/deploy # doesn't work
export PNGDIR=<workingdir>/sdks/build/png # doesn't work
It would be nice if someone could help me, I need this library to be compiled to use it, hope someone understood me.

Answer 1

Use CMAKE_PREFIX_PATH to indicate paths where find_library, find_path et al. should have a look (documentation)
Stuff like PNGDIR should no longer be used and is considered legacy that is kept for backwards compatibility. Patches for FindXXX provided by CMake to add XXX_DIR or XXX_ROOT are rejected by the CMake developers.