[CI] address remaining issues after workflows migration

[cz4rs]

• Add back clang-8 build once the workflow image is available. See #10: add missing bits for magistrate support workflows#11 (comment) for details.

• Enable address sanitizer in clang-11 and build-against-vt workflows:

 1/58 Test  #1: magistrate:main ................................................***Failed  Required regular expression not found. Regex=[PASSED
]  0.00 sec
==1293==ERROR: AddressSanitizer failed to allocate 0x0 (0) bytes of SetAlternateSignalStack (error code: 22)
==1293==Process memory map follows:
	0x000000400000-0x000000423000	/build/checkpoint/tests/main
	0x000000423000-0x0000005ad000	/build/checkpoint/tests/main
	0x0000005ad000-0x000000604000	/build/checkpoint/tests/main
	0x000000605000-0x000000606000	/build/checkpoint/tests/main
	0x000000606000-0x000000614000	/build/checkpoint/tests/main
	0x000000614000-0x000000f3b000	
	0x00007fff7000-0x00008fff7000	
	0x00008fff7000-0x02008fff7000	
	0x02008fff7000-0x10007fff8000	
	0x7fccb0e00000-0x7fccb1152000	
	0x7fccb11a8000-0x7fccb11c5000	
	0x7fccb11c5000-0x7fccb11ed000	/usr/lib/x86_64-linux-gnu/libc.so.6
	0x7fccb11ed000-0x7fccb1382000	/usr/lib/x86_64-linux-gnu/libc.so.6
	0x7fccb1382000-0x7fccb13da000	/usr/lib/x86_64-linux-gnu/libc.so.6
	0x7fccb13da000-0x7fccb13db000	/usr/lib/x86_64-linux-gnu/libc.so.6
	0x7fccb13db000-0x7fccb13df000	/usr/lib/x86_64-linux-gnu/libc.so.6
	0x7fccb13df000-0x7fccb13e1000	/usr/lib/x86_64-linux-gnu/libc.so.6
	0x7fccb13e1000-0x7fccb13ee000	
	0x7fccb13ee000-0x7fccb13f1000	/usr/lib/x86_64-linux-gnu/libgcc_s.so.1
	0x7fccb13f1000-0x7fccb1408000	/usr/lib/x86_64-linux-gnu/libgcc_s.so.1
	0x7fccb1408000-0x7fccb140c000	/usr/lib/x86_64-linux-gnu/libgcc_s.so.1
	0x7fccb140c000-0x7fccb140d000	/usr/lib/x86_64-linux-gnu/libgcc_s.so.1
	0x7fccb140d000-0x7fccb140e000	/usr/lib/x86_64-linux-gnu/libgcc_s.so.1
	0x7fccb140e000-0x7fccb141c000	/usr/lib/x86_64-linux-gnu/libm.so.6
	0x7fccb141c000-0x7fccb1498000	/usr/lib/x86_64-linux-gnu/libm.so.6
	0x7fccb1498000-0x7fccb14f3000	/usr/lib/x86_64-linux-gnu/libm.so.6
	0x7fccb14f3000-0x7fccb14f4000	/usr/lib/x86_64-linux-gnu/libm.so.6
	0x7fccb14f4000-0x7fccb14f5000	/usr/lib/x86_64-linux-gnu/libm.so.6
	0x7fccb14f5000-0x7fccb158f000	/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
	0x7fccb158f000-0x7fccb16a0000	/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
	0x7fccb16a0000-0x7fccb170f000	/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
	0x7fccb170f000-0x7fccb1710000	/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
	0x7fccb1710000-0x7fccb171b000	/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
	0x7fccb171b000-0x7fccb171e000	/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
	0x7fccb171e000-0x7fccb1721000	
	0x7fccb1722000-0x7fccb1726000	
	0x7fccb1726000-0x7fccb1728000	/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
	0x7fccb1728000-0x7fccb1752000	/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
	0x7fccb1752000-0x7fccb175d000	/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
	0x7fccb175d000-0x7fccb175e000	
	0x7fccb175e000-0x7fccb1760000	/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
	0x7fccb1760000-0x7fccb1762000	/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
	0x7ffd8409b000-0x7ffd840bc000	[stack]
	0x7ffd841d9000-0x7ffd841dd000	[vvar]
	0x7ffd841dd000-0x7ffd841df000	[vdso]
	0xffffffffff600000-0xffffffffff601000	[vsyscall]
==1293==End of process memory map.
==1293==AddressSanitizer CHECK failed: /build/llvm-toolchain-11-mnvtwk/llvm-toolchain-11-11.1.0/compiler-rt/lib/sanitizer_common/sanitizer_common.cpp:54 "((0 && "unable to mmap")) != (0)" (0x0, 0x0)

Originally posted by @cz4rs in #377 (comment)