Separate file for Makefile based building of smt2_incremental

So that the `.cpp` files for incremental SMT2 solving can be
added/removed/renamed without triggering codeowner review of the
`src/solvers` directory.

Author: thomasspriggs

src/solvers/Makefile

@@ -68,6 +68,8 @@ ifneq ($(CADICAL),)
   CP_CXXFLAGS += -DHAVE_CADICAL
 endif
 
+include smt2_incremental/Makefile
+
 SRC = $(BOOLEFORCE_SRC) \
       $(CHAFF_SRC) \
       $(CUDD_SRC) \
@@ -193,17 +195,7 @@ SRC = $(BOOLEFORCE_SRC) \
       smt2/smt2_parser.cpp \
       smt2/smt2_tokenizer.cpp \
       smt2/smt2irep.cpp \
-      smt2_incremental/convert_expr_to_smt.cpp \
-      smt2_incremental/smt_bit_vector_theory.cpp \
-      smt2_incremental/smt_commands.cpp \
-      smt2_incremental/smt_core_theory.cpp \
-      smt2_incremental/smt_logics.cpp \
-      smt2_incremental/smt_options.cpp \
-      smt2_incremental/smt_solver_process.cpp \
-      smt2_incremental/smt_sorts.cpp \
-      smt2_incremental/smt_terms.cpp \
-      smt2_incremental/smt_to_smt2_string.cpp \
-      smt2_incremental/smt2_incremental_decision_procedure.cpp \
+      $(SMT2_INCREMENTAL_SRC) \
       # Empty last line
 
 include ../common

src/solvers/smt2_incremental/Makefile

@@ -0,0 +1,14 @@
+
+SMT2_INCREMENTAL_SRC = \
+      smt2_incremental/convert_expr_to_smt.cpp \
+      smt2_incremental/smt_bit_vector_theory.cpp \
+      smt2_incremental/smt_commands.cpp \
+      smt2_incremental/smt_core_theory.cpp \
+      smt2_incremental/smt_logics.cpp \
+      smt2_incremental/smt_options.cpp \
+      smt2_incremental/smt_solver_process.cpp \
+      smt2_incremental/smt_sorts.cpp \
+      smt2_incremental/smt_terms.cpp \
+      smt2_incremental/smt_to_smt2_string.cpp \
+      smt2_incremental/smt2_incremental_decision_procedure.cpp \
+      # Empty last line