While build blis library using ninja generator on windows, observed
ninja is randomly adding "|| '(set', 'FAIL_LINE=3&', 'goto', ':ABORT)'"
as extra arguments for add_custom_command. Due to this flatten-headers
python script was failing to create blis.h and cblas.h headers.
Modified the python script to fix above issue.
AMD-Internal: [CPUPL-2748]
Change-Id: I83b753d08e46f94b282176fcc661ce34e5eee3cf