artoolkit: Also add time.h include #53

Job	Run time
build (win-libs-vc14-x64, Visual Studio 16 2019, Release, windows-2019, -A x64, thirdparty-win64....	22m 2s
build (win-libs-vc14, Visual Studio 16 2019, Release, windows-2019, -A Win32, thirdparty-win32.zip)	25m 45s
build (darwin-libs-a, Unix Makefiles, Release, macos-latest, -DCMAKE_OSX_ARCHITECTURES="arm64;x86...	19m 11s
build (android-libs-arm64, Unix Makefiles, Release, ubuntu-latest, -DCMAKE_TOOLCHAIN_FILE=$ANDROI...	15m 2s
build (android-libs-arm, Unix Makefiles, Release, ubuntu-latest, -DCMAKE_TOOLCHAIN_FILE=$ANDROID_...	15m 21s
build (android-libs-x86_64, Unix Makefiles, Release, ubuntu-latest, -DCMAKE_TOOLCHAIN_FILE=$ANDRO...	15m 22s
build (android-libs-x86, Unix Makefiles, Release, ubuntu-latest, -DCMAKE_TOOLCHAIN_FILE=$ANDROID_...	15m 15s
	2h 7m 58s

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