CMake: Fix how missing backends are handled

- Replace references to the deleted null_backend.py script with an error
  message in CMake.
- Add the missing pw_log_null module.

Change-Id: I7b279cff0c6cd61e97d9c3a622ffd37449319e31
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/44600
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
Commit-Queue: Wyatt Hepler <hepler@google.com>
4 files changed
tree: d02fb8bf5a2cf460867ad403743a8a8314cd4029
  1. build_overrides/
  2. docker/
  3. docs/
  4. pw_allocator/
  5. pw_analog/
  6. pw_arduino_build/
  7. pw_assert/
  8. pw_assert_basic/
  9. pw_assert_log/
  10. pw_base64/
  11. pw_bloat/
  12. pw_blob_store/
  13. pw_boot_armv7m/
  14. pw_build/
  15. pw_bytes/
  16. pw_checksum/
  17. pw_chrono/
  18. pw_chrono_embos/
  19. pw_chrono_freertos/
  20. pw_chrono_stl/
  21. pw_chrono_threadx/
  22. pw_cli/
  23. pw_containers/
  24. pw_cpu_exception/
  25. pw_cpu_exception_cortex_m/
  26. pw_docgen/
  27. pw_doctor/
  28. pw_env_setup/
  29. pw_fuzzer/
  30. pw_hdlc/
  31. pw_hex_dump/
  32. pw_i2c/
  33. pw_interrupt/
  34. pw_interrupt_cortex_m/
  35. pw_kvs/
  36. pw_libc/
  37. pw_log/
  38. pw_log_basic/
  39. pw_log_multisink/
  40. pw_log_null/
  41. pw_log_rpc/
  42. pw_log_sink/
  43. pw_log_tokenized/
  44. pw_malloc/
  45. pw_malloc_freelist/
  46. pw_metric/
  47. pw_minimal_cpp_stdlib/
  48. pw_module/
  49. pw_multisink/
  50. pw_package/
  51. pw_persistent_ram/
  52. pw_polyfill/
  53. pw_preprocessor/
  54. pw_presubmit/
  55. pw_protobuf/
  56. pw_protobuf_compiler/
  57. pw_random/
  58. pw_result/
  59. pw_ring_buffer/
  60. pw_router/
  61. pw_rpc/
  62. pw_snapshot/
  63. pw_span/
  64. pw_status/
  65. pw_stream/
  66. pw_string/
  67. pw_sync/
  68. pw_sync_baremetal/
  69. pw_sync_embos/
  70. pw_sync_freertos/
  71. pw_sync_stl/
  72. pw_sync_threadx/
  73. pw_sys_io/
  74. pw_sys_io_arduino/
  75. pw_sys_io_baremetal_lm3s6965evb/
  76. pw_sys_io_baremetal_stm32f429/
  77. pw_sys_io_stdio/
  78. pw_target_runner/
  79. pw_thread/
  80. pw_thread_embos/
  81. pw_thread_freertos/
  82. pw_thread_stl/
  83. pw_thread_threadx/
  84. pw_tokenizer/
  85. pw_tool/
  86. pw_toolchain/
  87. pw_trace/
  88. pw_trace_tokenized/
  89. pw_unit_test/
  90. pw_varint/
  91. pw_watch/
  92. pw_web_ui/
  93. targets/
  94. third_party/
  95. .bazelignore
  96. .bazelrc
  97. .clang-format
  98. .eslintrc.json
  99. .gitattributes
  100. .gitignore
  101. .gn
  102. .prettierrc.js
  103. .pylintrc
  104. activate.bat
  105. AUTHORS
  106. bootstrap.bat
  107. bootstrap.sh
  108. BUILD
  109. BUILD.gn
  110. BUILDCONFIG.gn
  111. CMakeLists.txt
  112. LICENSE
  113. modules.gni
  114. OWNERS
  115. package.json
  116. PW_PLUGINS
  117. README.md
  118. tsconfig.json
  119. WORKSPACE
  120. yarn.lock
README.md

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