BUILD: Add CMake option to build with Abseil

CMakeLists.txt

@@ -26,7 +26,7 @@ set(xoreos-tools_VERSION 0.0.6)
 # -------------------------------------------------------------------------
 # options!
 option(Boost_USE_STATIC_LIBS "Use Boost static libraries" OFF)
-
+option(GTest_HAS_ABSEIL "Use Abseil and RE2 for Google Test" OFF)
 
 # -------------------------------------------------------------------------
 # load some cmake modules from cmake/ subfolder
@@ -350,6 +350,13 @@ install(
 
 # -------------------------------------------------------------------------
 # unit tests, parsed from the Automake rules.mk files
+set(TEST_LIBRARIES ${XOREOSTOOLS_LIBRARIES})
+if(GTest_HAS_ABSEIL)
+  find_package(absl REQUIRED)
+  add_definitions(-DGTEST_HAS_ABSL)
+  list(APPEND TEST_LIBRARIES absl::container absl::debugging absl::flags absl::strings absl::types)
+endif()
+
 enable_testing()
 parse_automake(tests/rules.mk)