There is no rule for building the target “main.bc” required for “all”. Stop

[AoAnima]

Hi! Vlado, I'm sorry. When i do

$ cd build
$ sudo make install,

then a message appears:
make: *** There is no rule for building the target “main.bc” required for “all”. Stop.

$ more Makefile
EXTENSION = main
DATA = main--0.1.sql  # script files to install
# REGRESS = main_test     # our test script file (without extension)
MODULES = main          # our c module file to build

# postgres build stuff
PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)
include $(PGXS)

How to fix it tell me?