build BUGFIX building bison files

reflects recent changes in generating yang.y which is not in source, but build
directory.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8deba53..d596588 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -88,7 +88,7 @@
     configure_file(${PROJECT_SOURCE_DIR}/src/yang.y.in ${PROJECT_BINARY_DIR}/src/yang.y)
     add_custom_target(bison
         WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/src
-        COMMAND bison -l -o parser_yang_bis.c --defines=parser_yang_bis.h yang.y
+        COMMAND bison -l -o parser_yang_bis.c --defines=parser_yang_bis.h ${PROJECT_BINARY_DIR}/src/yang.y
         COMMAND flex -8 -L -o parser_yang_lex.c --header-file=parser_yang_lex.h yang.l
         COMMAND ${SED_TOOL} -i 's/int yychar\;/int yychar\;\\nchar *s = NULL, *tmp_s = NULL, *ext_name = NULL\;\\nstruct lys_module *trg = NULL\;\\nstruct lys_node *tpdf_parent = NULL, *data_node = NULL\;\\nstruct lys_ext_instance_complex *ext_instance = NULL\;\\nint is_ext_instance\;\\nvoid *actual = NULL\;\\nenum yytokentype backup_type, actual_type = MODULE_KEYWORD\;\\nint64_t cnt_val = 0\;\\nint is_value = 0\;\\nvoid *yang_type = NULL\;/' parser_yang_bis.c
     )