-posixtm.c: posixtm.y
- -bison -o posixtm.tab.c $(srcdir)/posixtm.y || yacc $(srcdir)/posixtm.y
- test ! -f y.tab.c || mv y.tab.c posixtm.tab.c
+# The artificial dependency on getdate.c keeps the two parsers from being
+# built in parallel. Enforcing this little bit of sequentiality lets
+# everyone (even those without bison) still run mostly parallel builds.
+posixtm.c: posixtm.y getdate.c
+ $(YACC) $(srcdir)/posixtm.y
+ mv y.tab.c posixtm.tab.c