Fixes build on systems using dash for default shell e.g.
errors like
run.do_strip.25842: [[: not found
| readelf: Error: Unable to read in 0x37 bytes of section headers
| readelf: Error: Not an ELF file - it has the wrong magic bytes at the start
Change-Id: I29cac15be44a02d75a3d6889b6ae9b2e19bf46af Signed-off-by: Khem Raj <raj.khem@gmail.com> Signed-off-by: Ross Burton <ross.burton@intel.com>