cmake(android): fix non-idempotent INSTALL scripts

cmake/OpenCVDetectAndroidSDK.cmake

@@ -348,9 +348,18 @@ macro(add_android_project target path)
     # put the final .apk to the OpenCV's bin folder
     add_custom_command(TARGET ${target} POST_BUILD COMMAND ${CMAKE_COMMAND} -E copy_if_different "${android_proj_bin_dir}/bin/${target}-debug.apk" "${OpenCV_BINARY_DIR}/bin/${target}.apk")
     if(INSTALL_ANDROID_EXAMPLES AND "${target}" MATCHES "^example-")
-      #apk
-      install(FILES "${OpenCV_BINARY_DIR}/bin/${target}.apk" DESTINATION "samples" COMPONENT samples)
       get_filename_component(sample_dir "${path}" NAME)
+      # apk
+      install(FILES "${OpenCV_BINARY_DIR}/bin/${target}.apk" DESTINATION "samples" COMPONENT samples)
+      # clear "external" project files (need to remove files generated by 'android' tool)
+      set(external_target_files ${ANDROID_PROJECT_FILES})
+      ocv_list_add_prefix(external_target_files "\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/samples/${sample_dir}/")
+      install(CODE "
+MESSAGE(STATUS \"Cleaning generated project files from Android sample install directory: ${sample_dir}\")
+FOREACH(f ${ANDROID_PROJECT_FILES})
+  FILE(REMOVE \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/samples/${sample_dir}/\${f}\")
+ENDFOREACH()
+" COMPONENT samples)
       #java part
       list(REMOVE_ITEM android_proj_files ${ANDROID_MANIFEST_FILE})
       foreach(f ${android_proj_files} ${ANDROID_MANIFEST_FILE})
@@ -368,11 +377,15 @@ macro(add_android_project target path)
       if(android_proj_lib_deps_commands)
         set(inst_lib_opt " --library ../../sdk/java")
       endif()
-      install(CODE "EXECUTE_PROCESS(COMMAND ${ANDROID_EXECUTABLE} --silent update project --path . --target \"${android_proj_sdk_target}\" --name \"${target}\" ${inst_lib_opt}
-                                    WORKING_DIRECTORY \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/samples/${sample_dir}\"
-                                   )"  COMPONENT samples)
-      #empty 'gen'
-      install(CODE "MAKE_DIRECTORY(\"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/samples/${sample_dir}/gen\")" COMPONENT samples)
+      install(CODE "
+MESSAGE(STATUS \"Fixing Android library reference for sample: ${sample_dir}\")
+EXECUTE_PROCESS(
+    COMMAND ${ANDROID_EXECUTABLE} --silent update project --path . --target \"${android_proj_sdk_target}\" --name \"${target}\" ${inst_lib_opt}
+    WORKING_DIRECTORY \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/samples/${sample_dir}\"
+)
+" COMPONENT samples)
+      # empty 'gen'
+      install(CODE "FILE(MAKE_DIRECTORY \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/samples/${sample_dir}/gen\")" COMPONENT samples)
     endif()
   endif()
 endmacro()