library not found for -lrt - c

Question

I am compiling a Makefile that needs -lrt library. My compiler is gcc-8 and I am currently working on a OSX Mojave OS.
I run from terminal using the make command, and I get the following error:
ld: library not found for -lrt
collect2: error: ld returned 1 exit status
make: *** [eflomal] Error 1
I have already tried to remove -lrt from LDFLAGS but in that case I get other errors:
/usr/local/Cellar/gcc/8.3.0/bin/gcc-8 -lm -lgomp -fopenmp eflomal.o -o eflomal
Undefined symbols for architecture x86_64:
"___kmpc_critical", referenced from:
_.omp_outlined..57 in eflomal.o
_.omp_outlined..61 in eflomal.o
"___kmpc_end_critical", referenced from:
_.omp_outlined..57 in eflomal.o
_.omp_outlined..61 in eflomal.o
"___kmpc_for_static_fini", referenced from:
_.omp_outlined. in eflomal.o
_.omp_outlined..57 in eflomal.o
_.omp_outlined..61 in eflomal.o
"___kmpc_for_static_init_4", referenced from:
_.omp_outlined. in eflomal.o
_.omp_outlined..57 in eflomal.o
_.omp_outlined..61 in eflomal.o
"___kmpc_fork_call", referenced from:
_main in eflomal.o
_align in eflomal.o
ld: symbol(s) not found for architecture x86_64
The Makefile header is the following:
export CXX=/usr/local/Cellar/gcc/8.3.0/bin/g++-8
export CC=/usr/local/Cellar/gcc/8.3.0/bin/gcc-8
CFLAGS=-Ofast -march=native -Wall --std=gnu99 -Wno-unused-function -g -fopenmp
# This is more suitable for debugging:
#CFLAGS=-Og -Wall --std=gnu99 -Wno-unused-function -g -fopenmp
#LDFLAGS=-lm -lrt -lgomp -fopenmp
LDFLAGS=-lm -lgomp -fopenmp -lrt
The first two lines are needed to use gcc compiler instead of clang (default on OSX).
Any idea on how to fix the problem?