target_dir_path: add `SpirvBuilder::target_dir_path` to set the targe… #281

Job	Run time
Test (windows-2022, x86_64-pc-windows-msvc)	30m 46s
Lint	6m 12s
Test (ubuntu-20.04, aarch64-linux-android, x86_64-unknown-linux-gnu)	7m 57s
Test (macOS-latest, x86_64-apple-darwin)	10m 43s
cargo-deny	1m 1s
Test (ubuntu-20.04, x86_64-unknown-linux-gnu)	15m 28s
test_success	3s
	1h 12m 10s

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