[cmake] Add llvm-dwarfdump to clang test dependencies

Commit r363496 ("[Clang] Harmonize Split DWARF options with llc",
2019-06-15) introduced the use of llvm-dwarfdump in the clang tests,
so ensure the clang tests are dependent on llvm-dwarfdump.

llvm-svn: 364021

clang/test/CMakeLists.txt

@@ -106,6 +106,7 @@ if( NOT CLANG_BUILT_STANDALONE )
     llvm-cat
     llvm-cxxfilt
     llvm-dis
+    llvm-dwarfdump
     llvm-lto2
     llvm-modextract
     llvm-nm