Add OVERRIDE_PACKAGE to crc32c and add -Wno-documentation-deprecated-sync to CMAKE_CXX_FLAGS instead of per-target

Author: raulcd

cpp/cmake_modules/ThirdpartyToolchain.cmake

@@ -3286,7 +3286,7 @@ function(build_crc32c_once)
       PARENT_SCOPE)
 
   fetchcontent_declare(crc32c
-                       ${FC_DECLARE_COMMON_OPTIONS}
+                       ${FC_DECLARE_COMMON_OPTIONS} OVERRIDE_FIND_PACKAGE
                        URL ${CRC32C_SOURCE_URL}
                        URL_HASH "SHA256=${ARROW_CRC32C_BUILD_SHA256_CHECKSUM}")
 
@@ -3411,18 +3411,14 @@ function(build_google_cloud_cpp_storage)
   set(BUILD_TESTING OFF)
   # Unity build causes some build errors.
   set(CMAKE_UNITY_BUILD FALSE)
-  fetchcontent_makeavailable(google_cloud_cpp)
 
   # Disable -Wdocumentation-deprecated-sync warning for google-cloud-cpp.
   if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-    foreach(_target google-cloud-cpp::storage google-cloud-cpp::rest_internal
-                    google-cloud-cpp::common)
-      if(TARGET ${_target})
-        target_compile_options(${_target} INTERFACE -Wno-documentation-deprecated-sync)
-      endif()
-    endforeach()
+    string(APPEND CMAKE_CXX_FLAGS " -Wno-documentation-deprecated-sync")
   endif()
 
+  fetchcontent_makeavailable(google_cloud_cpp)
+
   # Remove unused directories to save build directory storage.
   # 141MB -> 79MB
   file(REMOVE_RECURSE "${google_cloud_cpp_SOURCE_DIR}/ci")