[bazel] Rework liblldb (#91549)

Previously we were linking liblldb as a shared library, but also linking
the contents into the lldb binary. This is invalid and results in subtle
runtime issues because of duplicate constants, like the global plugin
registry. This now links the dylib to lldb directly. This requires we
switch to cc_binary instead because cc_shared_library expects your
library to export all symbols in your transitive dependency tree, where
we only want to export lldb symbols.

Author: keith

utils/bazel/llvm-project-overlay/lldb/BUILD.bazel

@@ -728,37 +728,64 @@ cc_library(
     ],
 )
 
-cc_library(
-    name = "liblldb.static",
-    deps = [
-        ":API",
-        ":Interpreter",
-    ],
+genrule(
+    name = "gen_exports_file_linux",
+    srcs = ["//lldb:source/API/liblldb-private.exports"],
+    outs = ["exports_linux.txt"],
+    cmd = """
+cat > $(OUTS) <<EOF
+{
+  global:
+    $$(sed 's/$$/;/g' $(SRCS))
+};
+EOF
+""",
 )
 
-cc_shared_library(
-    name = "liblldb",
-    # TODO: Remove once fixed https://github.com/bazelbuild/bazel/issues/21893
+genrule(
+    name = "gen_exports_file_macos",
+    srcs = ["//lldb:source/API/liblldb-private.exports"],
+    outs = ["exports_macos.txt"],
+    cmd = "sed 's/^/_/g' $(SRCS) > $(OUTS)",
+)
+
+# Create a shared library using linkshared=True for liblldb. This uses
+# cc_binary instead of cc_shared_library since the latter expects you to
+# re-export all transitive dependencies vs them being relinked into other
+# binaries.
+cc_binary(
+    name = "lldb{}".format(PACKAGE_VERSION),
     additional_linker_inputs = select({
+        "@platforms//os:linux": [
+            ":gen_exports_file_linux",
+        ],
         "@platforms//os:macos": [
-            ":HostMacOSXObjCXX",
-            "//lldb/source/Plugins:PluginPlatformMacOSXObjCXX",
+            ":gen_exports_file_macos",
         ],
         "//conditions:default": [],
     }),
-    shared_lib_name = select({
-        "@platforms//os:macos": "liblldb{}.dylib".format(PACKAGE_VERSION),
-        "@platforms//os:linux": "liblldb{}.so".format(PACKAGE_VERSION),
-    }),
-    # TODO: Remove once fixed https://github.com/bazelbuild/bazel/issues/21893
-    user_link_flags = select({
+    linkopts = select({
+        "@platforms//os:linux": [
+            "-Wl,--export-dynamic-symbol-list=$(location :gen_exports_file_linux)",
+        ],
         "@platforms//os:macos": [
-            "$(location :HostMacOSXObjCXX)",
-            "$(location //lldb/source/Plugins:PluginPlatformMacOSXObjCXX)",
+            "-Wl,-exported_symbols_list,$(location :gen_exports_file_macos)",
         ],
         "//conditions:default": [],
     }),
-    deps = [":liblldb.static"],
+    linkshared = True,
+    deps = [
+        ":API",
+        ":Interpreter",
+    ],
+)
+
+# cc_binary targets using linkshared=True to build a shared library cannot be
+# imported directly and instead need to be referenced indirectly through
+# cc_import
+cc_import(
+    name = "liblldb.wrapper",
+    shared_library = "lldb{}".format(PACKAGE_VERSION),
 )
 
 gentbl_cc_library(
@@ -794,7 +821,7 @@ cc_binary(
     deps = [
         ":APIHeaders",
         ":Host",
-        ":liblldb.static",
+        ":liblldb.wrapper",
         ":lldb_options_inc_gen",
         "//llvm:Option",
         "//llvm:Support",