add autotools cache file to .gitignore #193

Job	Run time
Run tests (ubuntu-20.04, true, sudo apt install -y -qq gfortran liblapack-dev libmetis-dev libnau...	4m 3s
Run tests (ubuntu-20.04, false, sudo apt install -y -qq gfortran liblapack-dev libmetis-dev libna...	4m 10s
Run tests (ubuntu-22.04, true, sudo apt install -y -qq gfortran liblapack-dev libmetis-dev libnau...	4m 36s
Run tests (ubuntu-22.04, false, sudo apt install -y -qq gfortran liblapack-dev libmetis-dev libna...	4m 18s
Run tests (macos-13, false, brew install metis bash, CC=clang OSX=13)	5m 27s
Run tests (macos-13, false, brew install metis bash, CC=gcc-13 CXX=g++-13 OSX=13 ADD_CXXFLAGS=-Wl...	8m 35s
Run tests (macos-14, false, brew install metis bash, arm64, CC=gcc-13 CXX=g++-13 OSX=14 ADD_CXXFL...	5m 26s
	36m 35s

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