Only expose include/nlohmann/json.hpp as public header

All other headers are not meant to be included by a client of this
library and should be declared in `srcs`.

BUILD.bazel

@@ -1,6 +1,6 @@
 cc_library(
     name = "json",
-    hdrs = [
+    srcs = [
         "include/nlohmann/adl_serializer.hpp",
         "include/nlohmann/byte_container_with_subtype.hpp",
         "include/nlohmann/detail/abi_macros.hpp",
@@ -41,12 +41,12 @@ cc_library(
         "include/nlohmann/detail/string_concat.hpp",
         "include/nlohmann/detail/string_escape.hpp",
         "include/nlohmann/detail/value_t.hpp",
-        "include/nlohmann/json.hpp",
         "include/nlohmann/json_fwd.hpp",
         "include/nlohmann/ordered_map.hpp",
         "include/nlohmann/thirdparty/hedley/hedley.hpp",
         "include/nlohmann/thirdparty/hedley/hedley_undef.hpp",
     ],
+    hdrs = ["include/nlohmann/json.hpp"],
     includes = ["include"],
     visibility = ["//visibility:public"],
     alwayslink = True,

cmake/scripts/gen_bazel_build_file.cmake

@@ -4,11 +4,12 @@ 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")
+list(REMOVE_ITEM HEADERS "include/nlohmann/json.hpp")
 
 file(WRITE "${BUILD_FILE}" [=[
 cc_library(
     name = "json",
-    hdrs = [
+    srcs = [
 ]=])
 
 foreach(header ${HEADERS})
@@ -17,6 +18,7 @@ endforeach()
 
 file(APPEND "${BUILD_FILE}" [=[
     ],
+    hdrs = ["include/nlohmann/json.hpp"],
     includes = ["include"],
     visibility = ["//visibility:public"],
     alwayslink = True,