Extend C++ project with CMakeList.txt - c++

Question

I'm trying to transform old project with Makefile to a modern one with CMakeLists.txt and GoogleTest framework but i can't handle the dependencies.
This is my Project structure
Project-LG
src/
app/
main.cpp
A.cpp
A.hpp
B.cpp
B.hpp
C.cpp
C.hpp
...
cpp-utils/
D.cpp
D.hpp
E.hpp
F.hpp
json/
json.hpp
hiredis/ /*Makefile project*/
orane2/ /*Makefile project*/
rmr/ /*Makefile project*/
spdlog/ /*Headers project with nested directories*/
Makefile
And this is the "Project-LG" Makefile
CC=gcc
CPP=g++
SRCDIR = .
APPDIR = $(SRCDIR)/app
UTILSDIR = $(SRCDIR)/cpp-utils
TARGETDIR =./../out
OBJDIR =./../out/obj
APP_OBJDIR =$(OBJDIR)/app
UTILS_OBJDIR =$(OBJDIR)/cpp-utils
LIBSDIR = ./../libs
INCLUDE_FILE = \
-Iapp \
-Icpp-utils \
-Irmr/si \
-Irmr/si/si95 \
-Irmr/common \
-Ijson \
-Iorane2 \
-I. \
-Ihiredis
SUBDIRS := \
$(SRCDIR)/rmr \
$(SRCDIR)/orane2 \
$(SRCDIR)/hiredis
LFLAGS =
LIBS += -pthread -static-libstdc++ \
-L$(LIBSDIR) -l:librmr.a -l:liborane2.a -l:hiredis.a
XAPP_NAME_STR := '"app-lg"'
CFLAGS += -Wall -g -O2 -DXAPP_NAME=$(XAPP_NAME_STR) $(INCLUDE_FILE)
CPPFLAGS = $(CFLAGS) -fPIC -std=c++17
APP_EXE ?= xapp
APP_SOURCES := $(shell find $(APPDIR) -maxdepth 1 -name '*.cpp' -printf '%f\n')
UTILS_SOURCES := $(shell find $(UTILSDIR) -maxdepth 1 -name '*.cpp' -printf '%f\n')
APP_OBJS := $(addprefix $(APP_OBJDIR)/, $(APP_SOURCES:%.cpp=%.o))
UTILS_OBJS := $(addprefix $(UTILS_OBJDIR)/, $(UTILS_SOURCES:%.cpp=%.o))
.SUFFIXES: .c~.o
.PHONY: all $(SUBDIRS) clean
all: $(SUBDIRS) $(APP_EXE)
$(APP_EXE): $(APP_OBJS) $(UTILS_OBJS)
#mkdir -p $(TARGETDIR)
#mkdir -p $(OBJDIR)
$(CPP) $(CFLAGS) $(LFLAGS) $(APP_OBJS) $(UTILS_OBJS) $(LIBS) -o $(TARGETDIR)/$#
$(APP_OBJDIR)/%.o : $(APPDIR)/%.cpp
#mkdir -p $(OBJDIR)
#mkdir -p $(APP_OBJDIR)
$(CPP) -c $(CPPFLAGS) $(LFLAGS) $< -o $#
$(UTILS_OBJDIR)/%.o : $(UTILSDIR)/%.cpp
#mkdir -p $(OBJDIR)
#mkdir -p $(UTILS_OBJDIR)
$(CPP) -c $(CPPFLAGS) $(LFLAGS) $< -o $#
$(SUBDIRS):
$(MAKE) -C $#
clean:
rm -rf $(TARGETDIR)
It was difficult to figure out how to call the Makefile from CMake and how to add the GoogleTest framework with all its dependencies
Please accept my thanks for your time.