Thank you for your help. That resolved the problem. My bad.
The build ran much further and then got another error, which I'll mention here, and go research it, since it could be just my bleeding edge source code.
cc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -Wno-unused-command-line-argument -I/usr/local/include -D_THREAD_SAFE -pthread -D_REENTRANT -D_THREAD_SAFE -D_POSIX_PTHREAD_SEMANTICS -fPIC -DPIC -I../include -I../../../../src/interfaces/ecpg/include -DFRONTEND -I../../../../src/include -DSO_MAJOR_VERSION=3 -c -o datetime.o datetime.c
datetime.c:332:1: error: conflicting types for 'PGTYPESdate_defmt_asc'
PGTYPESdate_defmt_asc(date * d, const char *fmt, const char *str)
^
/usr/local/include/pgtypes_date.h:24:12: note: previous declaration is here
extern int PGTYPESdate_defmt_asc(date *, const char *, char *);
^
1 error generated.
gmake[4]: *** [<builtin>: datetime.o] Error 1