Fixes bug in bpkg-install global check

Bug was caused by incorrect placement of quoute character, causing the result of a check to be incorrect.

lib/install/install.sh

@@ -341,7 +341,7 @@ bpkg_install_from_remote () {
     )"
 
     ## check if forced global
-    if [[ ! -"z $(echo -n "${json}" | bpkg-json -b | grep '\["global"\]' | awk '{ print $2 }' | tr -d '"')" ]]; then
+    if [[ ! -z "$(echo -n "${json}" | bpkg-json -b | grep '\["global"\]' | awk '{ print $2 }' | tr -d '"')" ]]; then
       needs_global=1
     fi