[lldb/Utility] Fix unspecified behavior.

Order of evaluation of the operands of any C++ operator [...] is
unspecified. This patch fixes the issue in Stream::Indent by calling the
function consecutively.

On my Windows setup, TestSettings.py fails because the function prints
the value first, followed by the indentation.

Expected result:
  MY_FILE=this is a file name with spaces.txt

Actual result:
MY_FILE  =this is a file name with spaces.txt