[libFuzzer] replace string_view with string to fix the bots. This is NFC, just slower. 
[libFuzzer] replace string_view with string to fix the bots. This is NFC, just slower. 

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@360717 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt