[travis] Install libzip for macos

.ci/travis/macos/before_install.sh

@@ -52,7 +52,8 @@ brew install \
     spatialindex \
     fastcgi \
     qtkeychain \
-    gnu-sed
+    gnu-sed \
+    libzip
 
 
 mkdir -p ${HOME}/Library/Python/3.6/lib/python/site-packages

.ci/travis/macos/install.sh

@@ -37,7 +37,8 @@ fcgi
 expat
 sqlite
 flex
-bison"
+bison
+libzip"
 
 full_prefixes=""
 for p in ${prefixes}; do