Add xharp checkout back #79

Job	Run time
build	13m 36s
test (BoxingTests.Kernel)	7m 41s
test (Cosmos.Compiler.Tests.TypeSystem.Kernel)	4m 11s
test (Cosmos.Compiler.Tests.Bcl.Kernel)	4m 29s
test (Cosmos.Compiler.Tests.Bcl.System.Kernel)	10m 21s
test (Cosmos.Compiler.Tests.Exceptions.Kernel)	2m 58s
test (Cosmos.Compiler.Tests.MethodTests.Kernel)	3m 2s
test (Cosmos.Compiler.Tests.SingleEchoTest.Kernel)	3m 5s
test (Cosmos.Kernel.Tests.Fat.Kernel)	14m 3s
test (Cosmos.Kernel.Tests.IO.Kernel)	8m 58s
test (SimpleStructsAndArraysTest.Kernel)	7m 36s
test (Cosmos.Kernel.Tests.DiskManager.Kernel)	9m 19s
test (GraphicTest.Kernel)	9m 29s
test (NetworkTest.Kernel)	3m 0s
test (AudioTests.Kernel)	8m 10s
test (MemoryOperationsTest.Kernel)	3m 22s
test (ProcessorTests.Kernel)	5m 45s
	1h 59m 5s

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