cmake: replace deps by system check and check deps

Author: Mizux

cmake/check_deps.cmake

@@ -0,0 +1,9 @@
+# CXX Test
+if(BUILD_TESTING)
+  if(NOT TARGET GTest::gtest)
+    message(FATAL_ERROR "Target GTest::gtest not available.")
+  endif()
+  if(NOT TARGET GTest::gtest_main)
+    message(FATAL_ERROR "Target GTest::gtest_main not available.")
+  endif()
+endif()

cmake/deps.cmake renamed to cmake/system_deps.cmake

@@ -12,3 +12,9 @@ if(NOT BUILD_pybind11)
   find_package(pybind11 REQUIRED)
 endif()
 
+# CXX Test
+if(BUILD_TESTING)
+  if(NOT BUILD_googletest AND NOT TARGET GTest::gtest_main)
+    find_package(GTest REQUIRED)
+  endif()
+endif()