Make protoc use upb_generator stage1 (#21317)

Closes #21317

COPYBARA_INTEGRATE_REVIEW=#21317 from mkruskal-google:protoc_stage1 8106568
PiperOrigin-RevId: 748751321

Author: mkruskal-google

BUILD.bazel

@@ -350,7 +350,15 @@ cc_binary(
     copts = COPTS,
     linkopts = LINK_OPTS,
     visibility = ["//visibility:public"],
-    deps = ["//src/google/protobuf/compiler:protoc_lib"],
+    deps = ["//src/google/protobuf/compiler:protoc_lib_stage1"],
+)
+
+cc_binary(
+    name = "protoc_stage0",
+    copts = COPTS,
+    linkopts = LINK_OPTS,
+    visibility = ["//:__subpackages__"],
+    deps = ["//src/google/protobuf/compiler:protoc_lib_stage0"],
 )
 
 cc_binary(
@@ -365,7 +373,7 @@ cc_binary(
     }),
     linkopts = LINK_OPTS,
     visibility = ["//visibility:public"],
-    deps = ["//src/google/protobuf/compiler:protoc_lib"],
+    deps = ["//src/google/protobuf/compiler:protoc_lib_stage1"],
 )
 
 ################################################################################

src/google/protobuf/compiler/BUILD.bazel

@@ -15,6 +15,10 @@ load("//bazel:upb_c_proto_library.bzl", "upb_c_proto_library")
 load("//bazel:upb_proto_reflection_library.bzl", "upb_proto_reflection_library")
 load("//build_defs:arch_tests.bzl", "aarch64_test", "x86_64_test")
 load("//build_defs:cpp_opts.bzl", "COPTS")
+load(
+    "//upb_generator:bootstrap_compiler.bzl",
+    "bootstrap_cc_library",
+)
 load("test_plugin_injection.bzl", "inject_plugin_paths")
 
 proto_library(
@@ -213,13 +217,13 @@ cc_library(
     ],
 )
 
-cc_library(
+bootstrap_cc_library(
     name = "protoc_lib",
     srcs = [
         "main.cc",
     ],
+    bootstrap_deps = ["//upb_generator/minitable:generator"],
     copts = COPTS,
-    strip_include_prefix = "/src",
     visibility = [
         "//:__pkg__",
         "//pkg:__pkg__",
@@ -239,7 +243,6 @@ cc_library(
         "//src/google/protobuf/compiler/python",
         "//src/google/protobuf/compiler/ruby",
         "//src/google/protobuf/compiler/rust",
-        "//upb_generator/minitable:generator_stage0",
         "@abseil-cpp//absl/log:initialize",
     ],
 )

upb_generator/bootstrap_compiler.bzl

@@ -14,9 +14,10 @@ load(
 )
 
 _stages = ["_stage0", "_stage1", ""]
-_protoc = "//:protoc"
 
-_extra_proto_path = "-I$$(dirname $(location @com_google_protobuf//:descriptor_proto_srcs))/../.. "
+_protoc = "//:protoc_stage0"
+
+_extra_proto_path = "-I$$(dirname $(location //:descriptor_proto_srcs))/../.. "
 
 # This visibility is used automatically for anything used by the bootstrapping process.
 _bootstrap_visibility = [
@@ -26,6 +27,7 @@ _bootstrap_visibility = [
     "//upb/reflection:__pkg__",
     "//upb:__pkg__",  # For the amalgamations.
     "//python/dist:__pkg__",  # For the Python source package.
+    "//:__pkg__",  # For protoc
 ]
 
 def _stage_visibility(stage, visibility):

upb_generator/minitable/BUILD

@@ -33,7 +33,10 @@ bootstrap_cc_library(
         "//upb_generator:plugin",
     ],
     copts = UPB_DEFAULT_CPPOPTS,
-    visibility = ["//pkg:__pkg__"],
+    visibility = [
+        "//pkg:__pkg__",
+        "//src/google/protobuf/compiler:__pkg__",
+    ],
     deps = [
         ":names",
         ":names_internal",