Fix mcsat-initial-var-order (#507) #403

Job	Run time
ubuntu-latest\|debug\|--enable-mcsat\|CC=gcc CXX=g++	8m 33s
ubuntu-latest\|debug\|--enable-mcsat\|CC=clang CXX=clang++	8m 41s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=gcc CXX=g++	3m 56s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=clang CXX=clang++	4m 14s
ubuntu-latest\|release\|--enable-mcsat\|CC=gcc CXX=g++	5m 16s
ubuntu-latest\|release\|--enable-mcsat\|CC=clang CXX=clang++	5m 54s
ubuntu-latest\|release\|--enable-thread-safety\|CC=gcc CXX=g++	2m 54s
ubuntu-latest\|release\|--enable-thread-safety\|CC=clang CXX=clang++	2m 41s
ubuntu-latest\|gcov\|--enable-mcsat\|CC=gcc CXX=g++	8m 12s
ubuntu-latest\|debug\|--enable-thread-safety --enable-mcsat\|CC=gcc CXX=g++	8m 27s
	58m 48s

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