Restore OPENDDS_XERCES3 removed in parent commit

Continue to provide OPENDDS_XERCES3 even though it
shouldn't be needed when using the toolchain file.

When there is no OPENDDS_XERCES3 value set, it runs
_opendds_find_xerces_for_ace() which doesn't work with
the format of XercesC_LIBRARY from find_package().

optimized;D:/a/OpenDDS/OpenDDS/vcpkg/installed/x64-windows/lib/xerces-c_3.lib;debug;D:/a/OpenDDS/OpenDDS/vcpkg/installed/x64-windows/debug/lib

Author: mitza-oci

.github/workflows/cmake.yml

@@ -354,6 +354,7 @@ jobs:
           -DOPENDDS_COMPILE_WARNINGS=WARNING^
           -DOPENDDS_ACE_TAO_SRC=${{ github.workspace }}\OpenDDS\build\ACE_TAO^
           -DOPENDDS_MPC=${{ github.workspace }}\MPC^
+          -DOPENDDS_XERCES3=${{ env.VCPKG_INSTALLED_DIR }}/x64-windows^
           -DCMAKE_TOOLCHAIN_FILE=${{ env.VCPKG_TOOLCHAIN_FILE }}^
           -DOPENDDS_SECURITY=TRUE^
           -DOPENDDS_BUILD_TESTS=TRUE^
@@ -415,6 +416,7 @@ jobs:
           -DOPENDDS_COMPILE_WARNINGS=WARNING^
           -DOPENDDS_ACE_TAO_SRC=${{ github.workspace }}\OpenDDS\build\ACE_TAO^
           -DOPENDDS_MPC=${{ github.workspace }}\MPC^
+          -DOPENDDS_XERCES3=${{ env.VCPKG_INSTALLED_DIR }}/x64-windows^
           -DCMAKE_TOOLCHAIN_FILE=${{ env.VCPKG_TOOLCHAIN_FILE }}^
           -DOPENDDS_SECURITY=TRUE^
           -DOPENDDS_BUILD_TESTS=TRUE^
@@ -473,6 +475,7 @@ jobs:
           -DOPENDDS_COMPILE_WARNINGS=WARNING^
           -DOPENDDS_ACE_TAO_SRC=${{ github.workspace }}\OpenDDS\build\ACE_TAO^
           -DOPENDDS_MPC=${{ github.workspace }}\MPC^
+          -DOPENDDS_XERCES3=${{ env.VCPKG_INSTALLED_DIR }}/x64-windows^
           -DCMAKE_TOOLCHAIN_FILE=${{ env.VCPKG_TOOLCHAIN_FILE }}^
           -DOPENDDS_SECURITY=TRUE^
           -DOPENDDS_BUILD_TESTS=TRUE^
@@ -530,6 +533,7 @@ jobs:
           -DOPENDDS_COMPILE_WARNINGS=WARNING^
           -DOPENDDS_ACE_TAO_SRC=${{ github.workspace }}\OpenDDS\build\ACE_TAO^
           -DOPENDDS_MPC=${{ github.workspace }}\MPC^
+          -DOPENDDS_XERCES3=${{ env.VCPKG_INSTALLED_DIR }}/x64-windows^
           -DCMAKE_TOOLCHAIN_FILE=${{ env.VCPKG_TOOLCHAIN_FILE }}^
           -DOPENDDS_SECURITY=TRUE^
           -DOPENDDS_BUILD_TESTS=TRUE^