json: move validation test data to dedicated directory

test/json-parse.sh.in

@@ -1,11 +1,12 @@
 #!/bin/sh
 
 validate="@CMAKE_CURRENT_BINARY_DIR@/json-validate"
+basedir="@CMAKE_CURRENT_SOURCE_DIR@/test/json/validate"
 
 count=0
 code=0
 
-for i in $(ls "@CMAKE_CURRENT_SOURCE_DIR@/test/json/good/"*);
+for i in $(ls "${basedir}/good/"*);
 do
     $validate $i 2>/dev/null 1>&2
 
@@ -19,7 +20,7 @@ do
     count=$((count+1))
 done
 
-for i in $(ls "@CMAKE_CURRENT_SOURCE_DIR@/test/json/bad/"*);
+for i in $(ls "${basedir}/bad/"*);
 do
     $validate $i 1>&2 2>/dev/null