Generate the dir_* build args and lists of modules

- Generate dir_* module variables in modules.gni using the modules.py
  script. This consolidates the various lists of modules into a single
  PIGWEED_MODULES list. It also gives projects a way to include all
  Pigweed code without relying on its top-level BUILD.gn file.
- Generate pw_modules, pw_module_tests, and pw_module_docs lists that
  provide the targets for the top-level pw_modules and pw_modules_tests
  groups and for the docs:module_docs target.
- Display a warning in Pigweed's gn gen if any pw_* directories are
  missing from PIGWEED_MODULES.
- Move the logic for excluding tests under certain conditions into the
  modules.

Change-Id: Ied6f72315159af0d0da04505f8a91438e8b959e4
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/77940
Reviewed-by: Anthony DiGirolamo <tonymd@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/build_overrides/pigweed.gni b/build_overrides/pigweed.gni
index 2c057872e..04ef3b1b4 100644
--- a/build_overrides/pigweed.gni
+++ b/build_overrides/pigweed.gni
@@ -17,4 +17,5 @@ declare_args() {
   dir_pigweed = "//"
 }
 
+# Import modules.gni, which generates the modules list.
 import("$dir_pigweed/modules.gni")