Guard JS modules behind HAVE_JS_BACKEND and disable library-for-ghci for stage1

- Guard GHC.HsToCore.Foreign.JavaScript import and ArchJavaScript pattern
  matches in dsFImport/dsFExport behind #if defined(HAVE_JS_BACKEND), matching
  the existing HAVE_INTERPRETER guard pattern for Wasm.

- Move 11 JS-related modules (GHC.HsToCore.Foreign.JavaScript, GHC.JS.*)
  from unconditional Exposed-Modules to the if flag(js-backend) section in
  ghc.cabal.in. These modules are only needed when the JS backend is enabled
  and were being compiled unconditionally in stage1 despite -js-backend.

- Set library-for-ghci: False in cabal.project.stage1. Stage1 never loads
  libraries interactively, so generating GHCi-compatible .o files from every
  .a archive is pure waste. Stage2 retains library-for-ghci: True.

Estimated stage1 build time savings: 3-7% on top of existing minimal-stage1.

Author: angerman

cabal.project.stage1

@@ -75,7 +75,7 @@ package *
 
 if !os(windows)
   package *
-    library-for-ghci: True
+    library-for-ghci: False
 
 package ghc
   flags: +bootstrap

compiler/GHC/HsToCore/Foreign/Decl.hs

@@ -20,7 +20,9 @@ import GHC.Data.FastString
 import GHC.Tc.Utils.Monad        -- temp
 
 import GHC.HsToCore.Foreign.C
+#if defined(HAVE_JS_BACKEND)
 import GHC.HsToCore.Foreign.JavaScript
+#endif
 #if defined(HAVE_INTERPRETER)
 import GHC.HsToCore.Foreign.Wasm
 #endif
@@ -136,9 +138,11 @@ dsFImport id co (CImport _ cconv safety mHeader spec) = do
   let cconv' = unLoc cconv
       safety' = unLoc safety
   case (platformArch platform, cconv') of
+#if defined(HAVE_JS_BACKEND)
     (ArchJavaScript, _) -> do
       (bs, h, c) <- dsJsImport id co spec cconv' safety' mHeader
       pure (bs, h, c, [])
+#endif
 #if defined(HAVE_INTERPRETER)
     (ArchWasm32, JavaScriptCallConv) ->
       dsWasmJSImport id co spec safety'
@@ -184,9 +188,11 @@ dsFExport :: Id                 -- Either the exported Id,
 dsFExport fn_id co ext_name cconv is_dyn = do
   platform <- getPlatform
   case (platformArch platform, cconv) of
+#if defined(HAVE_JS_BACKEND)
     (ArchJavaScript, _) -> do
       (h, c, ts) <- dsJsFExport fn_id co ext_name cconv is_dyn
       pure (h, c, ts, [fn_id], [])
+#endif
 #if defined(HAVE_INTERPRETER)
     (ArchWasm32, JavaScriptCallConv) ->
       dsWasmJSExport fn_id co ext_name

compiler/ghc.cabal.in

@@ -630,7 +630,6 @@ Library
         GHC.HsToCore.Foreign.C
         GHC.HsToCore.Foreign.Call
         GHC.HsToCore.Foreign.Decl
-        GHC.HsToCore.Foreign.JavaScript
         GHC.HsToCore.Foreign.Prim
         GHC.HsToCore.Foreign.Utils
 
@@ -681,16 +680,6 @@ Library
         GHC.Iface.Warnings
         GHC.IfaceToCore
         GHC.Iface.Type
-        GHC.JS.Ident
-        GHC.JS.Make
-        GHC.JS.Optimizer
-        GHC.JS.Opt.Expr
-        GHC.JS.Opt.Simple
-        GHC.JS.Ppr
-        GHC.JS.Syntax
-        GHC.JS.JStg.Syntax
-        GHC.JS.JStg.Monad
-        GHC.JS.Transform
         GHC.Linker.Types
         GHC.Linker.Config
         GHC.Linker.Dynamic
@@ -1097,9 +1086,20 @@ Library
             GHC.CmmToAsm.LA64.Regs
             GHC.CmmToAsm.Reg.Linear.LA64
 
-    -- JavaScript Backend (StgToJS)
+    -- JavaScript Backend (JS IR, foreign decl desugaring, StgToJS)
     if flag(js-backend)
         Exposed-Modules:
+            GHC.HsToCore.Foreign.JavaScript
+            GHC.JS.Ident
+            GHC.JS.Make
+            GHC.JS.Optimizer
+            GHC.JS.Opt.Expr
+            GHC.JS.Opt.Simple
+            GHC.JS.Ppr
+            GHC.JS.Syntax
+            GHC.JS.JStg.Syntax
+            GHC.JS.JStg.Monad
+            GHC.JS.Transform
             GHC.Driver.Config.StgToJS
             GHC.StgToJS
             GHC.StgToJS.Apply