BaseTools: Fix DSC LibraryClass precedence rule

BaseTools: Fix DSC LibraryClass precedence rule

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3965

Currently DSC LibraryClass precedence rule is not align with DSC Spec.

The expectation rule should be:
[LibraryClasses.$(ARCH)] < [LibraryClasses.Common.$(MODULE_TYPE)]

The actual behavior is:
[LibraryClasses.$(ARCH)] > [LibraryClasses.Common.$(MODULE_TYPE)]

This patch fixes the issue.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Long1 Huang <long1.huang@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Yuwei Chen <yuwei.chen@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>