ios does not seems to inherit form macos, so add a yacc rule there too

solenv/gbuild/platform/ios.mk

@@ -45,6 +45,7 @@ gb_GCCP := $(CC)
 gb_AR := ar
 gb_AWK := awk
 gb_CLASSPATHSEP := :
+gb_YACC := bison
 
 gb_OSDEFS := \
 	-D$(OS) \
@@ -134,6 +135,16 @@ define gb_Helper_convert_native
 $(1)
 endef
 
+# YaccObject class
+
+define gb_YaccObject__command
+$(call gb_Output_announce,$(2),$(true),YAC,3)
+$(call gb_Helper_abbreviate_dirs,\
+	mkdir -p $(dir $(3)) && \
+	$(gb_YACC) $(T_YACCFLAGS) --defines=$(4) -o $(3) $(1) )
+
+endef
+
 
 # CObject class