Benchmarks: Fix compile error with custom string type (#490) #1178

Job	Run time
Emscripten	4m 51s
Windows (-DSAMPLES_BACKEND=auto -DENABLE_PRECOMPILED_HEADERS=OFF)	8m 55s
Windows (-DSAMPLES_BACKEND=Win32_VK -DRMLUI_VK_DEBUG=ON)	6m 48s
Windows (-DSAMPLES_BACKEND=SDL_VK -DBUILD_LUA_BINDINGS_FOR_LUAJIT=ON)	7m 3s
Linux (clang, clang++, -DENABLE_PRECOMPILED_HEADERS=OFF -DSAMPLES_BACKEND=GLFW_GL2)	2m 32s
Linux (clang, clang++, -DSAMPLES_BACKEND=SDL_VK)	2m 1s
Linux (-DBUILD_TESTING=ON -DENABLE_PRECOMPILED_HEADERS=OFF, true)	4m 46s
Linux (-DNO_FONT_INTERFACE_DEFAULT=ON -DENABLE_LOTTIE_PLUGIN=ON -DSAMPLES_BACKEND=X11_GL2)	2m 17s
Linux (-DDISABLE_RTTI_AND_EXCEPTIONS=ON -DSAMPLES_BACKEND=SDL_GL2)	2m 10s
Linux (-DNO_THIRDPARTY_CONTAINERS=ON -DSAMPLES_BACKEND=SFML_GL2)	2m 56s
Linux (-DSAMPLES_BACKEND=SDL_VK -DRMLUI_VK_DEBUG=ON -DENABLE_PRECOMPILED_HEADERS=OFF -DCMAKE_BUIL...	3m 37s
macOS (-DSAMPLES_BACKEND=auto)	7m 4s
macOS (-DSAMPLES_BACKEND=GLFW_GL2)	6m 18s
	1h 1m 18s

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