Merge topic 'SystemTools-cleanups'

5d8af0d6 SystemTools: Optimize range loop in RelativePath method
815cc593 SystemTools: Optimize range loop in FindProgramPath method
ac8d2033 SystemTools: Optimize range loop in FindLibrary method
c7e3ab12 SystemTools: Optimize range loop in FindProgram method
8c9ca162 SystemTools: Optimize range loop in FindProgram method
9992f69b SystemTools: Optimize range loop in FindName method
d6235796 SystemTools: Optimize iterator lifetime in JoinPath
00a3a436 SystemTools: Update buffered env value string only on a change

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !138