ASan: Don't do leak checking

Sadly, we *know* we have benign leaks in hard-to-fix places. It would still
be valuable to fail CI if ASan detects anything *else* - out of bounds writes,
use-after-free, etc.

Disable the leak checker so we can mark ASan failures as CI-fatal.
Hopefully we can get get the leaks fixed or correctly-suppressed *some*time!

spread/build/ubuntu/task.yaml

@@ -87,6 +87,6 @@ execute: |
     echo "OVERRIDE_CONFIGURE_OPTIONS += -DCMAKE_CXX_COMPILER_LAUNCHER=ccache" >> debian/opts.mk
 
     # build and run tests
-    UBSAN_OPTIONS=halt_on_error=1 debian/rules build
+    UBSAN_OPTIONS=halt_on_error=1 ASAN_OPTIONS=detect_leaks=0 debian/rules build
 
     ccache --show-stats --zero-stats > ${CCACHE_DIR}/ccache.stats