deps/reftable: wire up library with CMake

Wire up the reftable library with CMake. At the current point in time
the library is not yet plugged into libgit2 itself.

deps/reftable/CMakeLists.txt

@@ -0,0 +1,27 @@
+add_library(reftable OBJECT ${SRC_REFTABLE})
+
+file(GLOB SRC_REFTABLE "*.c" "*.h")
+list(SORT SRC_REFTABLE)
+
+set_property(TARGET reftable PROPERTY C_STANDARD 99)
+target_sources(reftable PRIVATE ${SRC_REFTABLE})
+target_include_directories(reftable PRIVATE
+	include
+	"${PROJECT_BINARY_DIR}/src/util"
+	"${PROJECT_BINARY_DIR}/include"
+	"${PROJECT_SOURCE_DIR}/src/util"
+	"${PROJECT_SOURCE_DIR}/include"
+	${LIBGIT2_DEPENDENCY_INCLUDES}
+	${LIBGIT2_SYSTEM_INCLUDES}
+)
+
+# The reftable library is not warning-free, so we disable turning warnings into
+# errors.
+if(MSVC)
+        set_source_files_properties(block.c PROPERTIES COMPILE_FLAGS -WX-)
+        set_source_files_properties(blocksource.c PROPERTIES COMPILE_FLAGS -WX-)
+        set_source_files_properties(record.c PROPERTIES COMPILE_FLAGS -WX-)
+        set_source_files_properties(stack.c PROPERTIES COMPILE_FLAGS -WX-)
+        set_source_files_properties(table.c PROPERTIES COMPILE_FLAGS -WX-)
+        set_source_files_properties(writer.c PROPERTIES COMPILE_FLAGS -WX-)
+endif()