perf: reduce size of .lake/build/doc

DocGen4/Output.lean

@@ -117,8 +117,10 @@ def htmlOutputIndex (baseConfig : SiteBaseContext) : IO Unit := do
   let finalJson := toJson index
   let finalHeaderJson := toJson headerIndex
   -- The root JSON for find
-  FS.writeFile (declarationsBasePath / "declaration-data.bmp") finalJson.compress
-  FS.writeFile (declarationsBasePath / "header-data.bmp") finalHeaderJson.compress
+  let declarationDir := basePath / "declarations"
+  FS.createDirAll declarationDir
+  FS.writeFile (declarationDir / "declaration-data.bmp") finalJson.compress
+  FS.writeFile (declarationDir / "header-data.bmp") finalHeaderJson.compress
 
 /--
 The main entrypoint for outputting the documentation HTML based on an

DocGen4/Output/Base.lean

@@ -11,9 +11,11 @@ namespace DocGen4.Output
 open scoped DocGen4.Jsx
 open Lean System Widget Elab Process
 
-def basePath := FilePath.mk "." / ".lake" / "build" / "doc"
+
+def lakeBuildDir := FilePath.mk "." / ".lake" / "build"
+def basePath := lakeBuildDir / "doc"
 def srcBasePath := basePath / "src"
-def declarationsBasePath := basePath / "declarations"
+def declarationsBasePath := lakeBuildDir / "doc-data"
 
 /--
 The context used in the `BaseHtmlM` monad for HTML templating.

lakefile.lean

@@ -144,8 +144,8 @@ module_facet docs (mod) : FilePath := do
 -- TODO: technically speaking this target does not show all file dependencies
 target coreDocs : FilePath := do
   let exeJob ← «doc-gen4».fetch
-  let basePath := (←getWorkspace).root.buildDir / "doc"
-  let dataFile := basePath / "declarations" / "declaration-data-Lean.bmp"
+  let dataPath := (← getWorkspace).root.buildDir / "doc-data"
+  let dataFile := dataPath / "declaration-data-Lean.bmp"
   exeJob.bindSync fun exeFile exeTrace => do
     let trace ← buildFileUnlessUpToDate dataFile exeTrace do
       proc {
@@ -161,7 +161,7 @@ library_facet docs (lib) : FilePath := do
   let coreJob ← coreDocs.fetch
   let exeJob ← «doc-gen4».fetch
   -- Shared with DocGen4.Output
-  let basePath := (←getWorkspace).root.buildDir / "doc"
+  let basePath := (← getWorkspace).root.buildDir / "doc"
   let dataFile := basePath / "declarations" / "declaration-data.bmp"
   let staticFiles := #[
     basePath / "style.css",