diff --git a/lldb/CMakeLists.txt b/lldb/CMakeLists.txt
--- a/lldb/CMakeLists.txt
+++ b/lldb/CMakeLists.txt
@@ -31,15 +31,23 @@
 endif()
 
 if (LLDB_ENABLE_PYTHON)
-  execute_process(
-    COMMAND ${Python3_EXECUTABLE}
-        -c "import distutils.sysconfig; print(distutils.sysconfig.get_python_lib(True, False, ''))"
-    OUTPUT_VARIABLE LLDB_PYTHON_DEFAULT_RELATIVE_PATH
-    OUTPUT_STRIP_TRAILING_WHITESPACE)
+  if (NOT CMAKE_CROSSCOMPILING)
+    execute_process(
+      COMMAND ${Python3_EXECUTABLE}
+          -c "import distutils.sysconfig; print(distutils.sysconfig.get_python_lib(True, False, ''))"
+      OUTPUT_VARIABLE LLDB_PYTHON_DEFAULT_RELATIVE_PATH
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+    file(TO_CMAKE_PATH ${LLDB_PYTHON_DEFAULT_RELATIVE_PATH} LLDB_PYTHON_DEFAULT_RELATIVE_PATH)
+  endif ()
 
-  file(TO_CMAKE_PATH ${LLDB_PYTHON_DEFAULT_RELATIVE_PATH} LLDB_PYTHON_DEFAULT_RELATIVE_PATH)
   set(LLDB_PYTHON_RELATIVE_PATH ${LLDB_PYTHON_DEFAULT_RELATIVE_PATH}
     CACHE STRING "Path where Python modules are installed, relative to install prefix")
+  if ("${LLDB_PYTHON_RELATIVE_PATH}" STREQUAL "")
+    message(FATAL_ERROR
+      "Crosscompiling with python requires manually setting
+      LLDB_PYTHON_RELATIVE_PATH.")
+  endif ()
 endif ()
 
 if (LLDB_ENABLE_PYTHON OR LLDB_ENABLE_LUA)