use devel/gtest instead of this bundled gtest, which fails to compile
use system devel/fmt instead of bundled fmt

Index: CMakeLists.txt
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -530,7 +530,6 @@ if (_M_X86)
   add_subdirectory(Externals/Bochs_disasm)
 endif()
 add_subdirectory(Externals/cpp-optparse)
-add_subdirectory(Externals/fmt EXCLUDE_FROM_ALL)
 add_subdirectory(Externals/glslang)
 add_subdirectory(Externals/imgui)
 
@@ -748,8 +747,6 @@ include_directories("${PROJECT_BINARY_DIR}/Source/Core
 # Unit testing.
 #
 if(ENABLE_TESTS)
-  message(STATUS "Using static gtest from Externals")
-  add_subdirectory(Externals/gtest EXCLUDE_FROM_ALL)
 else()
   message(STATUS "Unit tests are disabled")
 endif()