Can you use Xerces-C as submodule if CMAKE did not find Xerces-C?

I am working with e57 file format and PCL:
https://github.com/dogod621/E57Converter

but I do not like to install a lot of dependency library when building the project,
so I use Xerces-C and libE57Format as submodules.

But I need to create a weird FindXercesC.cmake to achieve this:
(because libE57Format cmakeList will trying to find XercesC)

FindXercesC.cmake
```CMAKE
# Just for correctlly compile libE57Format, replace original FindXercesC
set ( XercesC_FOUND True )
set ( XercesC_INCLUDE_DIR
"${CMAKE_SOURCE_DIR}/Xerces-C/src/"
"${CMAKE_BINARY_DIR}/Xerces-C/src/")
```

Is using Xerces-C as a submodule make sense?
If that make sense, can you make Xerces-C as submodule if CMAKE did not find Xerces-C?
Please~~~ So I can remove that weird FindXercesC.cmake.... @@...

Start by reading the project's CMake dependency handling and the libE57Format CMakeLists mentioned in the issue, then inspect how Xerces-C is represented as a submodule. Check configuration and build behavior when CMake cannot find a system Xerces-C installation. Done means the project can use the submodule without the custom FindXercesC.cmake while preserving the existing dependency path.

Written by the indexing model from the issue text.