land bpf2go basic support for Variable and VariableSpec #1378

Job	Run time
Build and Lint	2m 33s
Build Documentation	21s
Run tests on arm64	30s
Run tests (mainline)	1m 10s
Run tests on previous stable Go	1m 43s
Run tests (stable)	1m 3s
Run tests (6.6)	1m 6s
Run tests (6.1)	1m 6s
Run tests (5.15)	1m 11s
Run tests (5.10)	1m 10s
Run tests (5.4)	1m 19s
Run tests (4.19)	1m 5s
Run tests (4.14)	1m 13s
Run tests (4.9)	1m 15s
	16m 45s

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