signal_dumper: Increase timeout under asan

Bug: http://b/322868540

With clang-r522817, signal_dumper takes longer than 120s with asan,
causing timeout.  Increase the timeout to 180s.

Test: TARGET_PRODUCT=armv8 TARGET_RELEASE=trunk_staging \
        TARGET_BUILD_VARIANT=eng \
        ./prebuilts/build-tools/path/linux-x86/python3 \
        ./art/test/testrunner/run_build_test_target.py -j100 art-asan
Change-Id: Ib1a601e34e8755ffb31e80a35e55e1b982207420