Refactor build of C++ for pygambit extension.

This refactors the build of the pygambit extension to create more granular libraries of the C++ code,
with the aim of reducing unnecessary re-builds when changes are made.

setup.py

@@ -30,25 +30,66 @@
 # with passing C++-specific flags when building the extension
 lrslib = ("lrslib", {"sources": glob.glob("src/solvers/lrs/*.c")})
 
-cppgambit = (
-    "cppgambit",
+cppgambit_include_dirs = ["src"]
+cppgambit_cflags = (
+    ["-std=c++17"] if platform.system() == "Darwin"
+    else ["/std:c++17"] if platform.system() == "Windows"
+    else []
+)
+
+cppgambit_core = (
+    "cppgambit_core",
+    {
+        "sources": glob.glob("src/core/*.cc"),
+        "obj_deps": {"": glob.glob("src/core/*.h") + glob.glob("src/core/*.imp")},
+        "include_dirs": cppgambit_include_dirs,
+        "cflags": cppgambit_cflags,
+    }
+)
+
+cppgambit_games = (
+    "cppgambit_games",
     {
-         "sources": (
-            glob.glob("src/core/*.cc") +
-            glob.glob("src/games/*.cc") +
-            glob.glob("src/games/agg/*.cc") +
-            [fn for fn in glob.glob("src/solvers/*/*.cc") if "enumpoly" not in fn]
-         ),
-         "include_dirs": ["src"],
-         "cflags": (
-             ["-std=c++17"] if platform.system() == "Darwin"
-             else ["/std:c++17"] if platform.system() == "Windows"
-             else []
-         )
+        "sources": glob.glob("src/games/*.cc") + glob.glob("src/games/agg/*.cc"),
+        "obj_deps": {
+            "": (
+                glob.glob("src/core/*.h") + glob.glob("src/core/*.imp") +
+                glob.glob("src/games/*.h") + glob.glob("src/games/*.imp") +
+                glob.glob("src/games/agg/*.h")
+            )
+        },
+        "include_dirs": cppgambit_include_dirs,
+        "cflags": cppgambit_cflags,
     }
 )
 
 
+def solver_library_config(library_name: str, paths: list) -> tuple:
+    return (
+        library_name,
+        {
+            "sources": [fn for solver in paths for fn in glob.glob(f"src/solvers/{solver}/*.cc")],
+            "obj_deps": {
+                "": (
+                    glob.glob("src/core/*.h") + glob.glob("src/games/*.h") +
+                    glob.glob("src/games/agg/*.h") +
+                    [fn for solver in paths for fn in glob.glob(f"src/solvers/{solver}/*.h")]
+                )
+            },
+            "include_dirs": cppgambit_include_dirs,
+            "cflags": cppgambit_cflags,
+        }
+    )
+
+
+cppgambit_bimatrix = solver_library_config("cppgambit_bimatrix",
+                                           ["linalg", "lp", "lcp", "enummixed"])
+cppgambit_liap = solver_library_config("cppgambit_liap", ["liap"])
+cppgambit_logit = solver_library_config("cppgambit_logit", ["logit"])
+cppgambit_gtracer = solver_library_config("cppgambit_gtracer", ["gtracer", "ipa", "gnm"])
+cppgambit_simpdiv = solver_library_config("cppgambit_simpdiv", ["simpdiv"])
+
+
 libgambit = setuptools.Extension(
     "pygambit.gambit",
     sources=["src/pygambit/gambit.pyx"],
@@ -101,7 +142,9 @@ def readme():
         "scipy",
         "deprecated",
     ],
-    libraries=[cppgambit, lrslib],
+    libraries=[cppgambit_bimatrix, cppgambit_liap, cppgambit_logit, cppgambit_simpdiv,
+               cppgambit_gtracer,
+               cppgambit_games, cppgambit_core, lrslib],
     package_dir={"": "src"},
     packages=["pygambit"],
     ext_modules=Cython.Build.cythonize(libgambit,