clang: upgrade to Clang 18 #8055

Job	Run time
Build tetragon	9m 27s
Test kernel 4.19-20240620.102250 / test group 0	26m 14s
Test kernel 6.1-20240620.102250 / test group 0	31m 15s
Test kernel 5.15-20240620.102250 / test group 0	36m 19s
Test kernel 5.4-20240620.102250 / test group 0	32m 27s
Test kernel 5.10-20240620.102250 / test group 0	34m 58s
Test kernel 6.6-20240620.102250 / test group 0	31m 22s
Test kernel bpf-next-20240624.013140 / test group 0	32m 54s
Test kernel rhel8.9-20240806.173325 / test group 0	31m 24s
post-test	2s
	4h 26m 22s

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