refactor: move main into Lake.Main which is not imported by Lake

Lake.lean

@@ -1,16 +1,29 @@
 /-
-Copyright (c) 2017 Microsoft Corporation. All rights reserved.
+Copyright (c) 2021 Microsoft Corporation. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Gabriel Ebner, Sebastian Ullrich, Mac Malone
+Authors: Mac Malone
 -/
+import Lake.Async
+import Lake.BuildBin
+import Lake.BuildModule
+import Lake.BuildMonad
+import Lake.BuildPackage
+import Lake.BuildTarget
+import Lake.BuildTargets
+import Lake.BuildTop
 import Lake.Cli
+import Lake.CliT
+import Lake.Compile
+import Lake.Git
+import Lake.Glob
+import Lake.Help
+import Lake.Init
+import Lake.LeanConfig
+import Lake.LeanVersion
+import Lake.Package
+import Lake.Resolve
 import Lake.SearchPath
-
-def main (args : List String) : IO UInt32 := do
-  try
-    Lake.setupLeanSearchPath
-    Lake.cli args
-    pure 0
-  catch e =>
-    IO.eprintln <| "error: " ++ toString e -- avoid "uncaught exception: ..."
-    pure 1
+import Lake.Target
+import Lake.Task
+import Lake.Trace
+import Lake.Version

Lake/Main.lean

@@ -0,0 +1,16 @@
+/-
+Copyright (c) 2017 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Gabriel Ebner, Sebastian Ullrich, Mac Malone
+-/
+import Lake.Cli
+import Lake.SearchPath
+
+def main (args : List String) : IO UInt32 := do
+  try
+    Lake.setupLeanSearchPath
+    Lake.cli args
+    pure 0
+  catch e =>
+    IO.eprintln <| "error: " ++ toString e -- avoid "uncaught exception: ..."
+    pure 1

examples/bootstrap/package.lean

@@ -7,6 +7,7 @@ def package : PackageConfig := {
   srcDir := FilePath.mk ".." / ".."
   oleanDir := "."
   leancArgs := #["-O3", "-DNDEBUG"]
+  binRoot := `Lake.Main
   linkArgs :=
     if Platform.isWindows then
       #["-Wl,--export-all"]

examples/bootstrap/package.sh

@@ -1 +1,3 @@
+set -ex
+${LAKE:-../../build/bin/lake} build-lib
 ${LAKE:-../../build/bin/lake} build-bin