test: suppress certain leaks reported by LSan

so we can run TEST-46 under sanitizers once again.

`systemd-homed` runs fsck on home directories, which reports a memory
leak we're not interested in. Let's introduce an LSan suppression file
to get around this. Since the patterns in the suppression file are
matched using basic substring match[0], they're a bit cumbersome, but
should get the work one.

[0] https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer#suppressions

Example leaks (as reported by TEST-46):
```
systemd-homed[1333]: =================================================================
systemd-homed[1333]: ==1333==ERROR: LeakSanitizer: detected memory leaks
systemd-homed[1333]: Direct leak of 24 byte(s) in 1 object(s) allocated from:
systemd-homed[1333]:     #0 0x7f0c8facccd1 in calloc (/usr/lib/clang/12.0.1/lib/linux/libclang_rt.asan-x86_64.so+0xf4cd1)
systemd-homed[1333]:     #1 0x558d9494ff67  (/usr/bin/fsck+0x3f67)
systemd-homed[1333]: Direct leak of 6 byte(s) in 1 object(s) allocated from:
systemd-homed[1333]:     #0 0x7f0c8fa906c1 in strdup (/usr/lib/clang/12.0.1/lib/linux/libclang_rt.asan-x86_64.so+0xb86c1)
systemd-homed[1333]:     #1 0x558d949518fd  (/usr/bin/fsck+0x58fd)
systemd-homed[1333]: SUMMARY: AddressSanitizer: 30 byte(s) leaked in 2 allocation(s).
systemd-homed[1337]: ==1337==WARNING: Symbolizer was blocked from starting itself!
systemd-homed[1337]: =================================================================
systemd-homed[1337]: ==1337==ERROR: LeakSanitizer: detected memory leaks
systemd-homed[1337]: Direct leak of 67584 byte(s) in 1 object(s) allocated from:
systemd-homed[1337]:     #0 0x7f01edb84b19  (/usr/lib/clang/12.0.1/lib/linux/libclang_rt.asan-x86_64.so+0xf4b19)
systemd-homed[1337]:     #1 0x7f01e8326829  (/usr/bin/../lib/libLLVM-12.so+0xb46829)
systemd-homed[1337]: SUMMARY: AddressSanitizer: 67584 byte(s) leaked in 1 allocation(s).
```

With the suppression file:
```
systemd-homed[1339]: -----------------------------------------------------
systemd-homed[1339]: Suppressions used:
systemd-homed[1339]:   count      bytes template
systemd-homed[1339]:       2         30 /bin/fsck$
systemd-homed[1339]: -----------------------------------------------------
systemd-homed[1343]: ==1343==WARNING: Symbolizer was blocked from starting itself!
systemd-homed[1343]: -----------------------------------------------------
systemd-homed[1343]: Suppressions used:
systemd-homed[1343]:   count      bytes template
systemd-homed[1343]:       1      67584 /lib/libLLVM
systemd-homed[1343]: -----------------------------------------------------
```

1 files changed, 15 insertions, 1 deletions

diff --git a/test/test-functions b/test/test-functions
index d3705653ae..a4b7efb5ec 100644
--- a/test/test-functions
+++ b/test/test-functions
@@ -778,9 +778,23 @@ if [[ ! -e "$ASAN_RT_PATH" ]]; then
     exit 1
 fi
 
+# Suppress certain leaks reported by LSan (either in external tools or bogus
+# ones)
+# Docs: # https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer#suppressions
+#
+# - fsck is called by systemd-homed and is reporting a leak we're not interested
+#   in
+# - libLLVM is a "side effect" caused by the previous fsck leak
+cat >/systemd-lsan.supp <<INNER_EOF
+leak:/bin/fsck$
+leak:/sbin/fsck$
+leak:/lib/libLLVM
+INNER_EOF
+
+DEFAULT_LSAN_OPTIONS=${LSAN_OPTIONS:-}:suppressions=/systemd-lsan.supp
 DEFAULT_ASAN_OPTIONS=${ASAN_OPTIONS:-strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1}
 DEFAULT_UBSAN_OPTIONS=${UBSAN_OPTIONS:-print_stacktrace=1:print_summary=1:halt_on_error=1}
-DEFAULT_ENVIRONMENT="ASAN_OPTIONS=\$DEFAULT_ASAN_OPTIONS UBSAN_OPTIONS=\$DEFAULT_UBSAN_OPTIONS"
+DEFAULT_ENVIRONMENT="ASAN_OPTIONS=\$DEFAULT_ASAN_OPTIONS UBSAN_OPTIONS=\$DEFAULT_UBSAN_OPTIONS LSAN_OPTIONS=\$DEFAULT_LSAN_OPTIONS"
 
 # As right now bash is the PID 1, we can't expect PATH to have a sane value.
 # Let's make one to prevent unexpected "<bin> not found" issues in the future