Properly detect changes in Rust code and recompile Rust libraries

Due to we need to substitude config for Rust builds (see #44762 for
details), the source dir is copied to the binary dir, but this is done
only once, so to detect changes in sources you need to run cmake,
without this patch.

Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>

rust/CMakeLists.txt

@@ -51,8 +51,20 @@ file(COPY ".cargo" DESTINATION "${CMAKE_CURRENT_BINARY_DIR}")
 function(add_rust_subdirectory src)
     set(dst "${CMAKE_CURRENT_BINARY_DIR}/${src}")
     message(STATUS "Copy ${src} to ${dst}")
-    file(COPY "${src}" DESTINATION "${CMAKE_CURRENT_BINARY_DIR}")
+    file(COPY "${src}" DESTINATION "${CMAKE_CURRENT_BINARY_DIR}"
+        PATTERN target EXCLUDE)
     add_subdirectory("${dst}" "${dst}")
+
+    # cmake -E copy* do now know how to exclude files
+    # but we need to exclude "target" folder from copying, if someone or semantic
+    # completion created it.
+    add_custom_target(${src}-update ALL
+        COMMAND ${CMAKE_COMMAND}
+            -DFROM=${src}
+            -DTO=${CMAKE_CURRENT_BINARY_DIR}
+            -P "${CMAKE_CURRENT_SOURCE_DIR}/copy_exclude.cmake"
+        WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+        VERBATIM)
 endfunction()
 
 add_rust_subdirectory (BLAKE3)

rust/copy_exclude.cmake

@@ -0,0 +1,2 @@
+file(COPY "${FROM}" DESTINATION "${TO}"
+    PATTERN target EXCLUDE)