-# List osl.h in the prerequisites to make sure we generate it before attempting
-# to run the compiler. This matters only when the .d file does not exist.
-%.o: %.c osl.h Makefile errtab.h
+# The files to generate before attempting to run the compiler. These
+# are the order-only prerequisites in the rule below.
+pre_deps := osl.h errtab.h oslfsck.lsg.h
+
+# The .d and .o files are both created from a single cc invocation.
+define CC_CMD