packaging: don't build internal api docs by default in dev shells

These are totally available and you can just turn them on, but they have
very bad dependency tracking and thus bloat incremental change times,
which is not really ok.

Change-Id: Iaa63ed18a789e74fcb757248cd24c3b194afcc80

flake.nix

@@ -385,7 +385,7 @@
               nix = pkgs.callPackage ./package.nix {
                 inherit stdenv officialRelease versionSuffix;
                 busybox-sandbox-shell = pkgs.busybox-sandbox-shell or pkgs.default-busybox-sandbox;
-                internalApiDocs = true;
+                internalApiDocs = false;
               };
               pre-commit = self.hydraJobs.pre-commit.${pkgs.system} or { };
             in

package.nix

@@ -392,6 +392,7 @@ stdenv.mkDerivation (finalAttrs: {
         bashInteractive,
         clang-tools,
         clangbuildanalyzer,
+        doxygen,
         glibcLocales,
         just,
         llvmPackages,
@@ -457,6 +458,10 @@ stdenv.mkDerivation (finalAttrs: {
               skopeo
               just
               nixfmt
+              # Included above when internalApiDocs is true, but we set that to
+              # false intentionally to save dev build time.
+              # To build them in a dev shell, you can set -Dinternal-api-docs=enabled when configuring.
+              doxygen
               # Load-bearing order. Must come before clang-unwrapped below, but after clang_tools above.
               stdenv.cc
             ]