build: add abseil as submodule

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "third_party/tiny_thread_pool"]
 	path = third_party/tiny_thread_pool
 	url = https://github.com/dnomd343/tiny_thread_pool.git
+[submodule "third_party/abseil-cpp"]
+	path = third_party/abseil-cpp
+	url = https://github.com/abseil/abseil-cpp.git

CMakeLists.txt

@@ -19,6 +19,17 @@ file(
     FOLLOW_SYMLINK_CHAIN
 )
 
+################################################################################
+
+option(BUILD_DYN "build shared klotski core library" OFF)
+if (BUILD_DYN)
+    add_compile_options(-fPIC)
+endif()
+
+set(ABSL_PROPAGATE_CXX_STD ON)
+include_directories(third_party/abseil-cpp)
+add_subdirectory(third_party/abseil-cpp)
+
 add_subdirectory(src)
 
 ################################################################################

src/CMakeLists.txt

@@ -6,4 +6,6 @@ add_subdirectory(klotski_core)
 include_directories(klotski_core)
 
 add_executable(cli main.c)
-target_link_libraries(cli PRIVATE klotski)
+target_link_libraries(cli PRIVATE klotski absl::flat_hash_map)
+
+# -labsl_hash -labsl_city -labsl_low_level_hash -labsl_raw_hash_set

src/klotski_core/CMakeLists.txt

@@ -6,13 +6,6 @@ project(klotski-core VERSION 0.1.2 LANGUAGES CXX)
 
 ################################################################################
 
-option(BUILD_DYN "build shared klotski core library" OFF)
-if (BUILD_DYN)
-    add_compile_options(-fPIC)
-endif()
-
-################################################################################
-
 macro(git_tag _tag)
     find_package(Git QUIET)
     if (GIT_FOUND)
@@ -104,10 +97,6 @@ include_directories(group)
 
 ################################################################################
 
-find_package(absl REQUIRED)
-
-################################################################################
-
 add_subdirectory(utils)
 add_subdirectory(all_cases)
 
@@ -151,10 +140,9 @@ list(APPEND OBJS $<TARGET_OBJECTS:group>)
 
 if (BUILD_DYN)
     add_library(klotski SHARED ${OBJS})
+    target_link_libraries(klotski absl::flat_hash_map)
 else()
     add_library(klotski STATIC ${OBJS})
 endif()
 
-target_link_libraries(klotski absl::flat_hash_map)
-
 ################################################################################

third_party/abseil-cpp

@@ -0,0 +1 @@
+Subproject commit b971ac5250ea8de900eae9f95e06548d14cd95fe