$NetBSD: patch-libraries_Cabal_Cabal-syntax_Cabal-syntax.cabal,v 1.1 2025/01/29 13:21:53 pho Exp $

Add a way to remove tool dependency on alex, otherwise it cannot be built
without having devel/alex preinstalled, which is impossible because
devel/alex cannot be built without GHC.

TODO: Upstream this.

--- libraries/Cabal/Cabal-syntax/Cabal-syntax.cabal.orig	2025-01-11 14:49:32.211381314 +0000
+++ libraries/Cabal/Cabal-syntax/Cabal-syntax.cabal
@@ -23,6 +23,13 @@ source-repository head
   location: https://github.com/haskell/cabal/
   subdir:   Cabal-syntax
 
+-- Hadrian is supposed to disable this flag because the user may be
+-- building from a source distribution where the parser has already been
+-- generated.
+Flag build-tool-depends
+    Description: Use build-tool-depends
+    Default: True
+
 library
   default-language: Haskell2010
   hs-source-dirs: src
@@ -56,7 +63,8 @@ library
   if impl(ghc >= 8.10)
     ghc-options: -Wunused-packages
 
-  build-tool-depends: alex:alex
+  if flag(build-tool-depends)
+    build-tool-depends: alex:alex
 
   exposed-modules:
     Distribution.Backpack