[MLIR:Python] Make MLIR Python targets buildable when LLVM is importe…

…d as an external dependency of TensorFlow.

Map @python_runtime to @local_config_python, and alias :runtime to :python_runtime in that package.

PiperOrigin-RevId: 407574863
Change-Id: I268bf205dce1ca50f30da7161e73145f25bec3c2

third_party/llvm/setup.bzl

@@ -7,4 +7,7 @@ def llvm_setup(name):
     llvm_disable_optional_support_deps()
 
     # Build @llvm-project from @llvm-raw using overlays.
-    llvm_configure(name = name)
+    llvm_configure(
+        name = name,
+        repo_mapping = {"@python_runtime": "@local_config_python"},
+    )

third_party/py/BUILD.tpl

@@ -54,6 +54,15 @@ cc_library(
     includes = ["python_include"],
 )
 
+# This alias is exists for the use of targets in the @llvm-project dependency,
+# which expect a python_headers target called @python_runtime//:headers. We use
+# a repo_mapping to alias python_runtime to this package, and an alias to create
+# the correct target.
+alias(
+    name = "headers",
+    actual = ":python_headers",
+)
+
 cc_library(
     name = "numpy_headers",
     hdrs = [":numpy_include"],