`LSAN_OPTIONS=malloc_context_size=1` results in all leaks being supressed

[sbc100]

We ended up patching LeakSuppressionContext::SuppressInvalid this in emscripten in order to avoid this issue:

https://github.com/emscripten-core/emscripten/blob/d8f677e301ca8877eae63940b934046f9376059b/system/lib/compiler-rt/lib/lsan/lsan_common.cpp#L186-L195

We advise users to use LSAN_OPTIONS=malloc_context_size=0 but this bug also effects anyone who sets it to 1. Basically if we limit the amount of stack frames we collect it causes GetCallerPC to return 0 for all leaks which in turn causes all leaks to be suppresed via SuppressInvalid.

While investigating I noticed that LSAN currently sets a lower limit of 1 for malloc_context_size (in FlagParser::parse_flags).. I suppose one possible solution to this issue would be to instead set this to 2.. since that is currently minimum required to get any leaks reported.