[Bazel] Support opt-driver library, like clang-driver

Author: wsmoses

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",