Fix up fuzzing test on Windows.

3bd112c fixed the fuzzing test on Linux, which, after
https://reviews.llvm.org/D125933, has one less branch. Turns out, on
Windows, that it still has the extra branch. I'm guessing that's because
exit() isn't known to be noreturn on Windows or something.

Either way, just make the test more tolerant.

compiler-rt/test/fuzzer/merge_two_step.test

@@ -10,7 +10,7 @@ RUN: echo ..Z... > %t/T1/3
 RUN: rm -f %t/MCF
 RUN: %run %t-FullCoverageSetTest -merge=1 -merge_control_file=%t/MCF %t/T0 %t/T1 2>&1 | FileCheck %s --check-prefix=CHECK1
 CHECK1: MERGE-OUTER: 3 files, 0 in the initial corpus
-CHECK1: MERGE-OUTER: 3 new files with {{.*}} new features added; 10 new coverage edges
+CHECK1: MERGE-OUTER: 3 new files with {{.*}} new features added; {{.*}} new coverage edges
 
 RUN: echo ...Z.. > %t/T2/1
 RUN: echo ....E. > %t/T2/2
@@ -28,4 +28,4 @@ CHECK2: MERGE-OUTER: starting merge from scratch, but reusing coverage informati
 CHECK2: MERGE-OUTER: 7 files, 0 in the initial corpus, 3 processed earlier
 CHECK2: MERGE-INNER: using the control file
 CHECK2: MERGE-INNER: 4 total files; 0 processed earlier; will process 4 files now
-CHECK2: MERGE-OUTER: 6 new files with {{.*}} new features added; 13 new coverage edges
+CHECK2: MERGE-OUTER: 6 new files with {{.*}} new features added; {{.*}} new coverage edges