Add DLL path for DDK3790 tool chain.

Reviewed-by: Liming Gao <liming.gao@intel.com>
Signed-off-by: Yu Wang <yu.wang@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2-buildtools/code/trunk/BaseTools@2656 c2973edb-eda0-4c78-bc6a-9341b269661f