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

[dogod621]

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

# 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.... @@...