validation: Fix shell quoting error in build_id assignment

- Fix spacing issue where AR variable was missing closing quote
- This caused build_AR value to be concatenated with "NM=" string
- Applied fix from Bitcoin PR bitcoin#31627 (commit 8a46286)
- Resolves reviewer feedback from knst and cursor[bot]

Addresses issue identified in review of PR #1068

Author: Claude Code

depends/Makefile

@@ -147,7 +147,7 @@ include packages/packages.mk
 #     2. Before including packages/*.mk (excluding packages/packages.mk), since
 #        they rely on the build_id variables
 #
-build_id:=$(shell env CC='$(build_CC)' C_STANDARD='$(C_STANDARD)' CXX='$(build_CXX)' CXX_STANDARD='$(CXX_STANDARD)' AR='$(build_AR) 'NM='$(build_NM)' RANLIB='$(build_RANLIB)' STRIP='$(build_STRIP)' SHA256SUM='$(build_SHA256SUM)' DEBUG='$(DEBUG)' LTO='$(LTO)' NO_HARDEN='$(NO_HARDEN)' ./gen_id '$(BUILD_ID_SALT)' 'GUIX_ENVIRONMENT=$(realpath $(GUIX_ENVIRONMENT))')
+build_id:=$(shell env CC='$(build_CC)' C_STANDARD='$(C_STANDARD)' CXX='$(build_CXX)' CXX_STANDARD='$(CXX_STANDARD)' AR='$(build_AR)' NM='$(build_NM)' RANLIB='$(build_RANLIB)' STRIP='$(build_STRIP)' SHA256SUM='$(build_SHA256SUM)' DEBUG='$(DEBUG)' LTO='$(LTO)' NO_HARDEN='$(NO_HARDEN)' ./gen_id '$(BUILD_ID_SALT)' 'GUIX_ENVIRONMENT=$(realpath $(GUIX_ENVIRONMENT))')
 $(host_arch)_$(host_os)_id:=$(shell env CC='$(host_CC)' C_STANDARD='$(C_STANDARD)' CXX='$(host_CXX)' CXX_STANDARD='$(CXX_STANDARD)' AR='$(host_AR)' NM='$(host_NM)' RANLIB='$(host_RANLIB)' STRIP='$(host_STRIP)' SHA256SUM='$(build_SHA256SUM)' DEBUG='$(DEBUG)' LTO='$(LTO)' NO_HARDEN='$(NO_HARDEN)' ./gen_id '$(HOST_ID_SALT)' 'GUIX_ENVIRONMENT=$(realpath $(GUIX_ENVIRONMENT))')
 
 boost_packages_$(NO_BOOST) = $(boost_packages)