Build: Restore -fshort-wchar flag for toolchain config

Removing the -fshort-wchar flag will cause link error with
RTX library while using armclang and debug mode.
This patch reverts changes in the commit
8bebd05745a8b27dccc6403f0215fa6e39de3bc1.

Change-Id: Iff165aa8b080d02f8fcfad07703ed3a274f346b0
Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>
1 file changed