py-tensorflow: fix linking with ubuntu's gcc (#45437)

gcc on ubuntu has fix-cortex-a53-843419 set by default - this causes linking
issues (symbol relocation errors) for tf, even when compiling for different
cpus.

var/spack/repos/builtin/packages/py-tensorflow/package.py

@@ -452,6 +452,22 @@ class PyTensorflow(Package, CudaPackage, ROCmPackage, PythonExtension):
     )
     phases = ["configure", "build", "install"]
 
+    def flag_handler(self, name, flags):
+        spec = self.spec
+        # ubuntu gcc has this workaround turned on by default in aarch64
+        # and it causes issues with symbol relocation during link
+        # note, archspec doesn't currently ever report cortex_a53!
+        if (
+            name == "ldflags"
+            and spec.target.family == "aarch64"
+            and "ubuntu" in spec.os
+            and spec.compiler.name == "gcc"
+            and "cortex_a53" not in spec.target.name
+        ):
+            flags.append("-mno-fix-cortex-a53-843419")
+
+        return (flags, None, None)
+
     # https://www.tensorflow.org/install/source
     def setup_build_environment(self, env):
         spec = self.spec