Fix confvar to sort variables before hashing

[Copilot]

The confvar function generates MD5 hashes of configuration variables to create stamp filenames for dependency tracking. Variable order affects the hash, causing spurious rebuilds when PKG_CONFIG_DEPENDS accumulates variables from different include files in non-deterministic order.

Change

Sort variables before hashing in rules.mk:

# Before
confvar=$(shell echo '$(foreach v,$(1),$(v)=$(subst ','\'',$($(v))))' | $(MKHASH) md5)

# After  
confvar=$(shell echo '$(foreach v,$(sort $(1)),$(v)=$(subst ','\'',$($(v))))' | $(MKHASH) md5)

This ensures identical variable sets produce identical hashes regardless of input order, preventing unnecessary rebuilds when the same configurations are specified in different sequences.

Original prompt

Please analyze the coe and find issues of the Makefile logic that cause rebuilding of packages even if no changes happened.

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