gcc: Don't use \t in sed as it's not POSIX compliant.

completions/gcc

@@ -38,9 +38,8 @@ _gcc()
         # sink stderr:
         # for C/C++/ObjectiveC it's useless
         # for FORTRAN/Java it's an error
-        COMPREPLY=( $( compgen -W "$( $cc --help 2>/dev/null | \
-           sed -e 's/\t/ /g' -e '/^  *-/!d' -e 's/ *-\([^][ <>]*\).*/-\1/' )" \
-           -- "$cur" ) )
+        COMPREPLY=( $( compgen -W "$( $cc --help 2>/dev/null | tr '\t' ' ' |\
+           sed -e '/^  *-/!d' -e 's/ *-\([^][ <>]*\).*/-\1/' )" -- "$cur" ) )
         [[ $COMPREPLY == *= ]] && compopt -o nospace
     else
         _filedir