Use official Apt respositories for LLVM CI #3413

Job	Run time
check_format	1m 35s
x86_64-gnu-test (1.7.3)	1s
x86_64-gnu-test-preview_mt	5m 44s
x86_64-gnu-test (1.8.2)	1s
x86_64-gnu-test (1.9.2)	1s
x86_64-musl-test	31m 9s
x86_64-gnu-test (1.10.1)	21m 45s
x86_64-gnu-test (1.11.2)	21m 21s
x86_64-gnu-test (1.12.2)	17m 31s
x86_64-gnu-test (1.13.3)	10m 58s
x86_64-gnu-test (1.14.0)	9m 37s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	26m 51s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	24m 52s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	7m 56s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	7m 46s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	4m 18s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	1m 13s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	1s
	3h 12m 40s

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