github: Add LSan workaround for tests on Ubuntu 20.04 again

This was removed with 0fea6a7f8e ("github: Adapt to switch to Ubuntu
22.04 for ubuntu-latest") as it didn't seem necessary anymore.  But
recently there have been such random crashes again with the 20.04 image.

.github/workflows/linux.yml

@@ -145,6 +145,8 @@ jobs:
       LEAK_DETECTIVE: ${{ matrix.leak-detective || 'no' }}
       CC: ${{ matrix.compiler || 'gcc' }}
       TEST: ${{ matrix.test }}
+      # LSan causes spurious SIGSEGV after tests due to DTLS handling by glibc
+      ASAN_OPTIONS: intercept_tls_get_addr=0
     steps:
       - uses: actions/checkout@v3
       - uses: actions/cache@v3