[llvm] [Bazel] Support opt-driver library, like clang-driver (PR #79205)

[William Moses via llvm-commits]

https://github.com/wsmoses created https://github.com/llvm/llvm-project/pull/79205

In Bazel, Clang current separates the clang executable into a clang-driver library, and the actual clang executable. This allows downstream users to make their own variations of clang, without having to redo/maintain separate build pipelines.

This adds the same for opt.

>From 1c9d5c6760a5d150e6c7c8478ae1fffe15741dcf Mon Sep 17 00:00:00 2001
From: "William S. Moses" <gh at wsmoses.com>
Date: Tue, 23 Jan 2024 15:17:10 -0500
Subject: [PATCH] [Bazel] Support opt-driver library, like clang-driver

---
 utils/bazel/llvm-project-overlay/llvm/BUILD.bazel | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/utils/bazel/llvm-project-overlay/llvm/BUILD.bazel b/utils/bazel/llvm-project-overlay/llvm/BUILD.bazel
index b22ec01376be6d4..21466a79af61b53 100644
--- a/utils/bazel/llvm-project-overlay/llvm/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/llvm/BUILD.bazel
@@ -4808,8 +4808,8 @@ cc_binary(
     ],
 )
 
-cc_binary(
-    name = "opt",
+cc_library(
+    name = "opt-driver",
     srcs = glob([
         "tools/opt/*.cpp",
         "tools/opt/*.h",
@@ -4820,7 +4820,6 @@ cc_binary(
         "@platforms//os:macos": [],
         "//conditions:default": ["-Wl,--export-dynamic"],
     }),
-    stamp = 0,
     deps = [
         ":AllTargetsAsmParsers",
         ":AllTargetsCodeGens",
@@ -4847,6 +4846,12 @@ cc_binary(
     ],
 )
 
+cc_binary(
+    name = "opt",
+    stamp = 0,
+    deps = [":opt-driver"]
+)
+
 gentbl(
     name = "SancovOptsTableGen",
     strip_include_prefix = "tools/sancov",