Build DX11 for a Windows 8.1 minimum #87

Job	Run time
build (x64-Debug, amd64)	1m 11s
build (x64-Release, amd64)	1m 29s
build (x64-Debug-Clang, amd64)	1m 26s
build (x64-Release-Clang, amd64)	1m 53s
build (x86-Debug, amd64_x86)	1m 41s
build (x86-Release, amd64_x86)	1m 32s
build (arm64-Debug, amd64_arm64)	1m 21s
build (arm64-Release, amd64_arm64)	1m 15s
build (arm64ec-Debug, amd64_arm64)	1m 3s
build (arm64ec-Release, amd64_arm64)	2m 12s
build (x86-Debug-Clang, amd64_x86)	1m 45s
build (x86-Release-Clang, amd64_x86)	1m 50s
build (arm64-Debug-Clang, amd64_arm64)	1m 6s
build (arm64-Release-Clang, amd64_arm64)	2m 20s
	22m 4s

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