Set `CMAKE_SYSTEM_NAME=Generic` for bare-metal systems #159

Job	Run time
Test (ubuntu-latest, stable)	28s
Rustfmt	14s
Test (ubuntu-latest, beta)	41s
Test (ubuntu-latest, nightly)	38s
Test (macos-latest, stable)	59s
Test (macos-latest, beta)	55s
Test (macos-latest, nightly)	57s
Test (windows-latest, stable)	2m 34s
Test (windows-latest, beta)	1m 48s
Test (windows-latest, nightly)	1m 31s
Test Cross Compile - aarch64-apple-ios	49s
Test Cross Compile - aarch64-unknown-linux-gnu	50s
Test Cross Compile - arm-unknown-linux-gnueabihf	55s
Test Cross Compile - mips-unknown-linux-gnu	16s
Test Cross Compile - mips64-unknown-linux-gnuabi64	18s
Test Cross Compile - mips64el-unknown-linux-gnuabi64	14s
Test Cross Compile - mipsel-unknown-linux-gnu	14s
Test Cross Compile - powerpc-unknown-linux-gnu	52s
Test Cross Compile - s390x-unknown-linux-gnu	1m 6s
Test Cross Compile - x86_64-unknown-linux-musl	1m 13s
Test Cross Compile - aarch64-unknown-linux-musl	1m 2s
Test Cross Compile - x86_64-pc-windows-gnu	1m 21s
Test Cross Compile - x86_64-unknown-freebsd	57s
Test Cross Compile - x86_64-unknown-netbsd	57s
Test Cross Compile - x86_64-sun-solaris	1m 9s
Test Cross Compile - x86_64-unknown-illumos	1m 9s
	24m 7s

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