Add semigroups to dependency for ghc <= 7

Hogeyama · Hogeyama · commit c66aee95552d · 2019-07-30T02:03:54.000+09:00
diff --git a/z3.cabal b/z3.cabal
@@ -60,6 +60,8 @@ Library
     Build-depends:       base >= 4.5 && <5,
                          containers,
                          transformers >= 0.2
+    if impl(ghc < 8)
+      Build-depends:     semigroups >= 0.5
 
     Build-tools:         hsc2hs
     Extensions:          FlexibleInstances
