Why is cmake reporting failure to find ICU components when using the default built-in transcoder?

Question

Below this paragraph is an example of how I am attempting to build with default transcoder on RHEL8 ( 4.18.0-477.27.1.el8_8.x86_64 ) with the GCC 12 toolset. Why would I need to specify more ICU variables with paths when using the built-in transcoder? I also wonder if it is a significant failure since it did generate outputs into the build directory.

# Setup location of Xerces binaries and where the XALANC binaries will be installed
export XERCESCROOT=/data/${USER}/repos/tp/xerces-c-3.2.4-install/release
export XALANCROOT=/data/${USER}/repos/tp/xalan_c-1.12-install/release

# Configure the build
 cmake -S /data/${USER}/repos/tp/xalan_c-1.12 \
   -B /data/${USER}/repos/tp/xalan_c-1.12/build \
   -DCMAKE_BUILD_TYPE=Release \
   -DCMAKE_INCLUDE_PATH=${XERCESCROOT}/include\
   -DCMAKE_LIBRARY_PATH=${XERCESCROOT}/lib \
   -DCMAKE_INSTALL_PREFIX=${XALANCROOT} \
   -DCMAKE_C_FLAGS=-O3 \
   -DCMAKE_CXX_FLAGS=-O3 

-- Found the following ICU libraries:
--   uc (required)
--   data (required)
--   i18n (required)
-- Failed to find all ICU components (missing: ICU_INCLUDE_DIR ICU_LIBRARY)