no, they can't be specified at all

Author: myk002

.github/workflows/build-linux.yml

@@ -131,7 +131,7 @@ jobs:
             -DBUILD_DOCS_NO_HTML:BOOL=${{ !inputs.html }} \
             -DBUILD_TESTS:BOOL=${{ inputs.tests }} \
             -DBUILD_XMLDUMP:BOOL=${{ inputs.xml-dump-type-sizes }} \
-            -DINSTALL_XMLDUMP:BOOL=${{ inputs.xml-dump-type-sizes }} \
+            ${{ inputs.xml-dump-type-sizes && '-DINSTALL_XMLDUMP:BOOL=1' || ''}} \
             -DINSTALL_DATA_FILES:BOOL=${{ inputs.common-files }} \
             -DINSTALL_SCRIPTS:BOOL=${{ inputs.common-files }}
       - name: Build DFHack

.github/workflows/build-windows.yml

@@ -95,7 +95,8 @@ jobs:
             win-msvc
       - name: Cross-compile
         env:
-          CMAKE_EXTRA_ARGS: '-DBUILD_LIBRARY=${{ inputs.platform-files }} -DBUILD_STONESENSE:BOOL=${{ inputs.stonesense }} -DBUILD_DOCS:BOOL=${{ inputs.docs }} -DBUILD_DOCS_NO_HTML:BOOL=${{ !inputs.html }} -DINSTALL_DATA_FILES:BOOL=${{ inputs.common-files }} -DINSTALL_SCRIPTS:BOOL=${{ inputs.common-files }} -DBUILD_DFLAUNCH:BOOL=${{ inputs.launchdf }} -DBUILD_TESTS:BOOL=${{ inputs.tests }} -DBUILD_XMLDUMP:BOOL=${{ inputs.xml-dump-type-sizes }} -DINSTALL_XMLDUMP:BOOL=${{ inputs.xml-dump-type-sizes }}'
+          XMLDUMP_ARG: ${{ inputs.xml-dump-type-sizes && '-DINSTALL_XMLDUMP:BOOL=1' || '' }}
+          CMAKE_EXTRA_ARGS: '-DBUILD_LIBRARY=${{ inputs.platform-files }} -DBUILD_STONESENSE:BOOL=${{ inputs.stonesense }} -DBUILD_DOCS:BOOL=${{ inputs.docs }} -DBUILD_DOCS_NO_HTML:BOOL=${{ !inputs.html }} -DINSTALL_DATA_FILES:BOOL=${{ inputs.common-files }} -DINSTALL_SCRIPTS:BOOL=${{ inputs.common-files }} -DBUILD_DFLAUNCH:BOOL=${{ inputs.launchdf }} -DBUILD_TESTS:BOOL=${{ inputs.tests }} -DBUILD_XMLDUMP:BOOL=${{ inputs.xml-dump-type-sizes }} ${XMLDUMP_ARG}'
         run: |
           cd build
           bash -x build-win64-from-linux.sh