Changing musl Makefile to use -O0 explicitly causes arm64 STLXR -> LDAXR pair to fail on real machines

[Sengming]

In case anyone makes this mistake like I did. This will cause atomic arm64 instructions STLXR and LDAXR in a_fetch_and() or a_fetch_or() musl functions to fail and get stuck in an infinite loop. These are called in malloc().

popcorn-compiler/lib/musl-1.1.18/Makefile

Line 121 in b009131

$(OPTIMIZE_SRCS:$(srcdir)/%.c=obj/%.o) $(OPTIMIZE_SRCS:$(srcdir)/%.c=obj/%.lo): CFLAGS += -O3