[libFuzzer] Disable dataflow.test on AArch64.

[morehouse]

Summary

After my recent change to allow MSan + libFuzzer, the
ExplodeDFSanLabelsTest.cpp test started to overflow the stack with
recursive function SetBytesForLabel() on an AArch64 bot. Perhaps that
bot has a smaller stack size, or maybe AArch64 has larger stack frames
for this particular function.

[morehouse]

@kcc: Do we want to just disable this test for AArch64, or should we change SetBytesForLabel to not be recursive?

[morehouse]

Note that I can reproduce this locally by compiling with -O0.

[kcc]

It it bothers someone, we can turn this function into a non-recursive by implementing a fixed-size queue (array of 2^16 shorts).
Or you can run the ExplodeDFSanLabelsTestDF with a large value of "ulimit -s".

It's fine for me to just disable this test on non-linux-x86_64

compiler-rt/trunk/test/fuzzer/dataflow.test

 # Tests the data flow tracer.
 REQUIRES: linux
+UNSUPPORTED: aarch64
 
 # Build the tracer and the test.
 RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fsanitize=dataflow  %S/../../lib/fuzzer/dataflow/DataFlow.cpp -o  %t-DataFlow.o
 RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -fsanitize-coverage=trace-pc-guard,pc-table,func,trace-cmp   %S/ThreeFunctionsTest.cpp     %t-DataFlow.o -o %t-ThreeFunctionsTestDF
 RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -fsanitize-coverage=trace-pc-guard,pc-table,func,trace-cmp   %S/ExplodeDFSanLabelsTest.cpp %t-DataFlow.o -o %t-ExplodeDFSanLabelsTestDF
 RUN: %cpp_compiler %S/ThreeFunctionsTest.cpp -o %t-ThreeFunctionsTest
 
 # Dump the function list.