Add Bazel build support (#3709)

cmake/scripts/gen_bazel_build_file.cmake

@@ -0,0 +1,24 @@
+# generate Bazel BUILD file
+
+set(PROJECT_ROOT "${CMAKE_CURRENT_LIST_DIR}/../..")
+set(BUILD_FILE "${PROJECT_ROOT}/BUILD.bazel")
+
+file(GLOB_RECURSE HEADERS LIST_DIRECTORIES false RELATIVE "${PROJECT_ROOT}" "include/*.hpp")
+
+file(WRITE "${BUILD_FILE}" [=[
+cc_library(
+    name = "json",
+    hdrs = [
+]=])
+
+foreach(header ${HEADERS})
+    file(APPEND "${BUILD_FILE}" "        \"${header}\",\n")
+endforeach()
+
+file(APPEND "${BUILD_FILE}" [=[
+    ],
+    includes = ["include"],
+    visibility = ["//visibility:public"],
+    alwayslink = True,
+)
+]=])