Fixing macos CI

[zkytony]

This fixes error encountered with macOS CI (example run: https://github.com/h2r/pomdp-py/actions/runs/18796751957/job/53637789176?pr=85)

g++ -g -w -O3 -I./MathLib -I./Algorithms -I./Algorithms/HSVI -I./Algorithms/SARSOP -I./Models/MOMDP/ -I./Models/MOMDP/CoLoc/ -I./OfflineSolver/ -I./Bounds/ -I./Core/ -I./Parser/Cassandra/ -I./Parser/Cassandra/include -I./Parser/ -I./Parser/POMDPX/ -I./Utils/ -I./Simulator/ -I./Evaluator/ -I./Controller/  -msse2      -c -o PolicyGraph/PolicyGraph.o PolicyGraph/PolicyGraph.cpp
clang++: error: unsupported option '-msse2' for target 'arm64-apple-darwin24.6.0'
make: *** [PolicyGraph/PolicyGraph.o] Error 1

by building pomdp-solve and sarsop from source on the now arm64-based macos-latest runner (github docs).