[DFSan] Increase size of buffer to fix possibly-flakey test.

[browneee]

Summary

Observed a test failure where "Returned length: 3054".

[browneee]

Increasing size and adding comment.

[browneee]

Switch large stack allocation to use malloc.

Update expected line numbers.

[browneee]

Fix formatting.

compiler-rt/test/dfsan/origin_stack_trace.c

int main(int argc, char *argv[]) {
   // CHECK: Origin value: {{.*}}, Taint value was stored to memory at
   // CHECK: #0 {{.*}} in main {{.*}}origin_stack_trace.c:[[@LINE-4]]
 
   // CHECK: Origin value: {{.*}}, Taint value was created at
   // CHECK: #0 {{.*}} in bar.dfsan {{.*}}origin_stack_trace.c:[[@LINE-19]]
   // CHECK-COUNT-8: #{{[0-9]+}} {{.*}} in bar.dfsan {{.*}}origin_stack_trace.c:[[@LINE-22]]
   // CHECK: #9 {{.*}} in baz.dfsan {{.*}}origin_stack_trace.c:[[@LINE-16]]
 
-  char buf[3000];
+  // Test logic expects this buffer to be large enough.
+  // String contains current paths, which could vary in length.
+  // Make this buffer much larger than necessary to accomodate variation.
+  char buf[8192];
   size_t length = dfsan_sprint_origin_trace(&c, NULL, buf, sizeof(buf));
 
   printf("==OUTPUT==\n\n%s==EOS==\n", buf);
   // CHECK: ==OUTPUT==
   // CHECK: Taint value 0x1 {{.*}} origin tracking ()
   // CHECK: Origin value: {{.*}}, Taint value was stored to memory at
   // CHECK: #0 {{.*}} in main {{.*}}origin_stack_trace.c:[[@LINE-18]]