--- a/src/libunicode/CMakeLists.txt
+++ b/src/libunicode/CMakeLists.txt
@@ -122,7 +122,7 @@ endif()
 if(LIBUNICODE_NEEDS_TABLEGEN)
     # Unified C++ tablegen: self-contained, no library dependencies.
     # Generates all 9 UCD source files in a single invocation.
-    add_executable(unicode_tablegen
+    set(_tablegen_srcs
         tablegen/tablegen_main.cpp
         tablegen/ucd_parser.cpp
         tablegen/enum_generator.cpp
@@ -130,17 +130,33 @@ if(LIBUNICODE_NEEDS_TABLEGEN)
         tablegen/case_norm_generator.cpp
         tablegen/multistage_generator.cpp
     )
-    set_target_properties(unicode_tablegen PROPERTIES CMAKE_BUILD_TYPE Release)
-    target_compile_definitions(unicode_tablegen PRIVATE LIBUNICODE_UCD_VERSION="${LIBUNICODE_UCD_VERSION}")
-    target_include_directories(unicode_tablegen PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/..)
+    if(CMAKE_CROSSCOMPILING)
+        # build time generator, built for the build host
+        set(HOST_CXX c++ CACHE STRING "C++ compiler for build time tools")
+        set(_tablegen "${CMAKE_CURRENT_BINARY_DIR}/unicode_tablegen.host")
+        add_custom_command(
+            OUTPUT ${_tablegen}
+            COMMAND ${HOST_CXX} -std=c++20 -O2 "-DLIBUNICODE_UCD_VERSION=\"${LIBUNICODE_UCD_VERSION}\""
+                -I${CMAKE_CURRENT_SOURCE_DIR}/.. ${_tablegen_srcs} -o ${_tablegen}
+            WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+            DEPENDS ${_tablegen_srcs}
+            VERBATIM
+        )
+    else()
+        add_executable(unicode_tablegen ${_tablegen_srcs})
+        set_target_properties(unicode_tablegen PROPERTIES CMAKE_BUILD_TYPE Release)
+        target_compile_definitions(unicode_tablegen PRIVATE LIBUNICODE_UCD_VERSION="${LIBUNICODE_UCD_VERSION}")
+        target_include_directories(unicode_tablegen PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/..)
+        set(_tablegen unicode_tablegen)
+    endif()
 
     add_custom_command(
         OUTPUT ${_LIBUNICODE_GENERATED_FILES}
-        COMMAND unicode_tablegen
+        COMMAND ${_tablegen}
             "${LIBUNICODE_UCD_DIR}"
             "${CMAKE_CURRENT_SOURCE_DIR}"
             "unicode::precompiled"
-        DEPENDS unicode_tablegen
+        DEPENDS ${_tablegen}
         COMMENT "Generating all UCD tables from ${LIBUNICODE_UCD_DIR}"
         VERBATIM
         USES_TERMINAL