Allow for old versions of bytestring

BS.dropEnd requires >=bytestring-0.11.1, but this doesn't get bundled
with GHC until v9.2.1. Allow for old bytestring/behavior so that
previous versions of GHC can still use haskell-updater.

Signed-off-by: hololeap <hololeap@users.noreply.github.com>

Distribution/Gentoo/GHC.hs

@@ -236,12 +236,17 @@ checkLibDirs v thisGhc libDirs =
 
     isValid dir = any (`isGhcLibDir` dir) libDirs
 
+#if MIN_VERSION_bytestring(1,11,1)
     -- Correct the path for hadrian-based installations
     -- See https://github.com/gentoo-haskell/haskell-updater/issues/20
     thisGhc' = if BS.isSuffixOf (BS.pack "/lib") thisGhc then BS.dropEnd 4 thisGhc else thisGhc
 
     -- Invalid if it's this GHC
     isInvalid fp = fp == thisGhc' || BS.isPrefixOf (thisGhc' `BS.snoc` pathSeparator) fp
+#else
+    -- Versions of GHC with old 'bytestring' can use the old behavior
+    isInvalid fp = fp == thisGhc || BS.isPrefixOf (thisGhc `BS.snoc` pathSeparator) fp
+#endif
 
 -- A valid GHC library directory starting at libdir has a name of
 -- "ghc", then a hyphen and then a version number.

haskell-updater.cabal

@@ -63,11 +63,15 @@ executable haskell-updater
   autogen-modules:  Paths_haskell_updater
   build-depends:
     , base        >=4.12 && <5
-    , bytestring  >=0.11.1.0
+    , bytestring
     , Cabal       >=1.8
     , containers
     , directory   >=1.2.5.0
     , filepath
     , process
 
+  -- Only force new bytestring on versions of GHC that come bundled with it
+  if impl(ghc >= 9.2.1)
+    build-depends:
+      , bytestring  >=0.11.1.0
   default-language: Haskell2010