[CMake] Teach CMake to build the maxsat example as an external

project. The project can be built by building the new `c_maxsat_example`
target.

examples/maxsat/CMakeLists.txt

@@ -0,0 +1,42 @@
+################################################################################
+# Example maxsat project
+################################################################################
+# NOTE: Even though this is a C project, libz3 uses C++. When using libz3
+# as a static library if we don't configure this project to also support
+# C++ we will use the C linker rather than the C++ linker and will not link
+# the C++ standard library in resulting in a link failure.
+project(Z3_C_MAXSAT_EXAMPLE C CXX)
+cmake_minimum_required(VERSION 2.8.12)
+find_package(Z3
+  REQUIRED
+  CONFIG
+  # `NO_DEFAULT_PATH` is set so that -DZ3_DIR has to be passed to find Z3.
+  # This should prevent us from accidently picking up an installed
+  # copy of Z3. This is here to benefit Z3's build sytem when building
+  # this project. When making your own project you probably shouldn't
+  # use this option.
+  NO_DEFAULT_PATH
+)
+message(STATUS "Z3_FOUND: ${Z3_FOUND}")
+message(STATUS "Found Z3 ${Z3_VERSION_STRING}")
+message(STATUS "Z3_DIR: ${Z3_DIR}")
+
+add_executable(c_maxsat_example maxsat.c)
+target_include_directories(c_maxsat_example PRIVATE ${Z3_C_INCLUDE_DIRS})
+target_link_libraries(c_maxsat_example PRIVATE ${Z3_LIBRARIES})
+
+if ("${CMAKE_SYSTEM_NAME}" MATCHES "[Ww]indows")
+  # On Windows we need to copy the Z3 libraries
+  # into the same directory as the executable
+  # so that they can be found.
+  foreach (z3_lib ${Z3_LIBRARIES})
+    message(STATUS "Adding copy rule for ${z3_lib}")
+    add_custom_command(TARGET c_maxsat_example
+      POST_BUILD
+      COMMAND
+        ${CMAKE_COMMAND} -E copy_if_different
+        $<TARGET_FILE:${z3_lib}>
+        $<TARGET_FILE_DIR:c_maxsat_example>
+    )
+  endforeach()
+endif()