llvm-isel-fuzzer: Add link-time dependency on BitWriter

This should fix the undefined reference to WriteBitcodeToFile here:
http://bb.pgr.jp/builders/i686-mingw32-RA-on-linux/builds/31682

(Why does every different bot seem to have a different level of
finickiness about LLVM_LINK_COMPONENTS?)

llvm-svn: 312345
diff --git a/llvm/tools/llvm-isel-fuzzer/CMakeLists.txt b/llvm/tools/llvm-isel-fuzzer/CMakeLists.txt
index 6b930fe..21f3d14 100644
--- a/llvm/tools/llvm-isel-fuzzer/CMakeLists.txt
+++ b/llvm/tools/llvm-isel-fuzzer/CMakeLists.txt
@@ -3,6 +3,7 @@
     Analysis
     AsmPrinter
     BitReader
+    BitWriter
     CodeGen
     Core
     FuzzMutate