pg_regress doesn't see it and you don't get any port-specific
comparisons.
# $(srcdir) to the build directory.
ifdef VPATH
-remaining_files_src := $(wildcard $(srcdir)/sql/*.sql) $(wildcard $(srcdir)/expected/*.out)
+remaining_files_src := $(wildcard $(srcdir)/sql/*.sql) $(wildcard $(srcdir)/expected/*.out) $(srcdir)/resultmap
remaining_files_build := $(patsubst $(srcdir)/%, $(abs_builddir)/%, $(remaining_files_src))
all: $(remaining_files_build)