Figure out a way to make cartogram and it's tests compile separately

[adisidev]

Currently, I was getting the following compile error upon trying to compile using the CMakeLists.txt on 03b29e7

AILED: CMakeFiles/test_string_to_decimal_converter.dir/tests/test_string_to_decimal_converter.cpp.o 
/opt/homebrew/opt/llvm@17/bin/clang++ -DBOOST_ALL_NO_LIB -DBOOST_UNIT_TEST_FRAMEWORK_DYN_LINK -I/Users/adi/Desktop/github/cartogram-cpp/include -I/Users/adi/Desktop/github/cartogram-cpp/PkgConfig::fftw -isystem /opt/homebrew/anaconda3/include -isystem /opt/homebrew/Cellar/fftw/3.3.10_1/include -I/opt/flex/flex-2.6.4/include -I/opt/bison/bison-3.7.91/share/include -O3 -DNDEBUG -std=gnu++20 -arch arm64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.5.sdk -isystem /opt/homebrew/anaconda3/include -ffp-contract=off -Wall -Wextra -pedantic -Wno-deprecated-declarations -MD -MT CMakeFiles/test_string_to_decimal_converter.dir/tests/test_string_to_decimal_converter.cpp.o -MF CMakeFiles/test_string_to_decimal_converter.dir/tests/test_string_to_decimal_converter.cpp.o.d -o CMakeFiles/test_string_to_decimal_converter.dir/tests/test_string_to_decimal_converter.cpp.o -c /Users/adi/Desktop/github/cartogram-cpp/tests/test_string_to_decimal_converter.cpp
In file included from /Users/adi/Desktop/github/cartogram-cpp/tests/test_string_to_decimal_converter.cpp:3:
In file included from /opt/homebrew/anaconda3/include/boost/test/unit_test.hpp:18:
In file included from /opt/homebrew/anaconda3/include/boost/test/test_tools.hpp:54:
In file included from /opt/homebrew/anaconda3/include/boost/test/tools/fpc_op.hpp:19:
In file included from /opt/homebrew/anaconda3/include/boost/test/tools/fpc_tolerance.hpp:19:
In file included from /opt/homebrew/anaconda3/include/boost/test/tree/decorator.hpp:22:
In file included from /opt/homebrew/anaconda3/include/boost/test/tree/fixture.hpp:21:
In file included from /opt/homebrew/anaconda3/include/boost/function/function0.hpp:11:
In file included from /opt/homebrew/anaconda3/include/boost/function/detail/maybe_include.hpp:15:
In file included from /opt/homebrew/anaconda3/include/boost/function/function_template.hpp:13:
In file included from /opt/homebrew/anaconda3/include/boost/function/detail/prologue.hpp:17:
In file included from /opt/homebrew/anaconda3/include/boost/function/function_base.hpp:21:
In file included from /opt/homebrew/anaconda3/include/boost/type_index.hpp:29:
In file included from /opt/homebrew/anaconda3/include/boost/type_index/stl_type_index.hpp:47:
/opt/homebrew/anaconda3/include/boost/container_hash/hash.hpp:131:33: error: no template named 'unary_function' in namespace 'std'; did you mean '__unary_function'?
  131 |         struct hash_base : std::unary_function<T, std::size_t> {};
      |                            ~~~~~^
/opt/homebrew/opt/llvm@17/bin/../include/c++/v1/__functional/unary_function.h:46:1: note: '__unary_function' declared here
   46 | using __unary_function = __unary_function_keep_layout_base<_Arg, _Result>;
      | ^
1 error generated.

I fixed this with conda install boost and conda update boost. This I feel is weird inherently, where is python coming from?

To avoid such issues, @nihalzp suggested we could create a flag in the CMakeLists.txt that would run/compile the tests conditionally.