Handle hadrian-based GHC installations

with an ugly hack

fixes #20

Distribution/Gentoo/GHC.hs

@@ -236,8 +236,12 @@ checkLibDirs v thisGhc libDirs =
 
     isValid dir = any (`isGhcLibDir` dir) libDirs
 
+    -- 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
+    isInvalid fp = fp == thisGhc' || BS.isPrefixOf (thisGhc' `BS.snoc` pathSeparator) fp
 
 -- A valid GHC library directory starting at libdir has a name of
 -- "ghc", then a hyphen and then a version number.