Replace git submodules with CMake FetchContent_Declare

.gitmodules

@@ -1,9 +1,3 @@
-[submodule "extlib/tlx"]
-	path = extlib/tlx
-	url = https://github.com/tlx/tlx
-[submodule "extlib/utils"]
-	path = extlib/utils
-	url = https://github.com/pasta-toolbox/utils
 [submodule "extlib/doxygen-awesome-css"]
 	path = extlib/doxygen-awesome-css
 	url = https://github.com/jothepro/doxygen-awesome-css.git

CMakeLists.txt

@@ -18,11 +18,13 @@
 #
 ################################################################################
 
-cmake_minimum_required(VERSION 3.4.1 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.24 FATAL_ERROR)
 
 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+include(FetchContent)
+
 project(pasta_bit_vector)
 
 # Options when compiling pasta::bit_vector
@@ -36,16 +38,19 @@ option(PASTA_BIT_VECTOR_BUILD_BENCHMARKS
 option(PASTA_BIT_VECTOR_COVERAGE_REPORTING
   "Enable coverage reporting for pasta::bit_vector" OFF)
 
-# Add tlx subdirectory only, if it has not been added by another project already
-if(NOT TARGET tlx)
-  add_subdirectory(extlib/tlx)
-endif()
+FetchContent_Declare(
+  tlx
+  GIT_REPOSITORY https://github.com/tlx/tlx.git
+  GIT_TAG        b6af589 #release 0.6.1
+)
 
-# Add pasta::utils subdirectory only, if it has not been added by another
-# project already
-if (NOT TARGET pasta_utils)
-  add_subdirectory(extlib/utils)
-endif()
+FetchContent_Declare(
+  pasta_utils
+  GIT_REPOSITORY https://github.com/pasta-toolbox/utils.git
+  GIT_TAG        92828b8 #main
+)
+
+FetchContent_MakeAvailable(tlx pasta_utils)
 
 # Optional code coverage (library compile options are only set if coverage
 # reporting is enabled