BaseTools: Create ".cache" folder when initialize Build object

BaseTools: Create ".cache" folder when initialize Build object

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1986

Create "Conf/.cache" folder as early as possible
so that the later code do need to check
if it exits and then create it.

Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>