buildgcc: Get the clean and correct uname on Cygwin

Running `uname` on Cygwin gets "CYGWIN_NT-6.1-WOW" instead of "Cygwin".
We need to fix the $UNAME on Cygwin.

Change-Id: I540bfc52089951006fd0e20bb9893a3d891df9e1
Signed-off-by: Zheng Bao <zheng.bao@amd.com>
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: http://review.coreboot.org/11124
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
1 file changed