[compiler-rt] Fix merge-posix.test file size test

Author: ndrewh

compiler-rt/test/fuzzer/merge-posix.test

@@ -14,7 +14,7 @@ RUN: echo ....U. > %tmp/T2/2
 RUN: echo ...Z.. > %tmp/T2/3
 RUN: echo ...Z.. > %tmp/T2/4
 RUN: echo ....E. > %tmp/T2/5
-RUN: echo .....R > %tmp/T2/6
+RUN: (echo .....R; for i in {1..1024}; do echo -n X; done) > %tmp/T2/6
 
 # Check that we can report an error if file size exceeded
 RUN: (ulimit -f 1; not %run %t-FullCoverageSetTest -merge=1 %tmp/T1 %tmp/T2 2>&1 | FileCheck %s --check-prefix=SIGXFSZ)