BaseTools: Add error condition for the path in PACKAGES_PATH env

BaseTools: Add error condition for the path in PACKAGES_PATH env

This patch adds two error conditions:
1) if one path in PACKAGES_PATH doesn't exist.
2) if the space exists in the PACKAGES_PATH.

In V2, highlight one path in PACKAGES_PATH env doesn't exist.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Yonghong Zhu <yonghong.zhu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed by: Andrew Fish <afish@apple.com>