BaseTools: add '-p' for Linux 'cp' command.

BaseTools: add '-p' for Linux 'cp' command.

Currently BaseTools use 'cp' command for PcdValueInit and GenMake
process, as the command can not keep the time info of the source
file, which will cause incremental build issue in Linux system,
thus the '-p' need be added to keep the source file's attributes
in copy process.

This patch fixes this issue.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Signed-off-by: Yuwei Chen <yuwei.chen@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>