[Bash-completion] Fixed a bug that ~ doesn't expanded to $HOME

Summary: `~/build/bin/clang -f[tab]` was executed without ~ expanded to $HOME, so changed this by expanding ~ to path using eval.

Differential Revision: https://reviews.llvm.org/D34925

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@306957 91177308-0d34-0410-b5e6-96231b3b80d8

utils/bash-autocomplete.sh

@@ -24,7 +24,9 @@ _clang()
     arg="$w2=,$cur"
   fi
 
-  flags=$( "${COMP_WORDS[0]}" --autocomplete="$arg" 2>/dev/null )
+  # expand ~ to $HOME
+  eval local path=${COMP_WORDS[0]}
+  flags=$( "$path" --autocomplete="$arg" 2>/dev/null )
   # If clang is old that it does not support --autocomplete,
   # fall back to the filename completion.
   if [[ "$?" != 0 ]]; then