Add link flags for grpc armv7 wheels (#62779)

* Add -lexecinfo for grpc armv7 wheel building

Add missing flags so that we can link grpc armv7 builds. This is needed because
home assistant wheel building installs libexecinfo which grpc recognizes
and uses for `backtrace`. This is normally provided by the standard library but
is not provided by alpine / musl.

This allows building a grpc 1.43.0 wheel on alpine 3.14 armv7 with python 3.9

* Fix quoting error in workflow wheels

.github/workflows/wheels.yml

@@ -42,6 +42,10 @@ jobs:
             echo "GRPC_PYTHON_BUILD_SYSTEM_OPENSSL=true"
             echo "GRPC_PYTHON_BUILD_WITH_CYTHON=true"
             echo "GRPC_PYTHON_DISABLE_LIBC_COMPATIBILITY=true"
+            # GRPC on armv7 needs -lexecinfo (issue #56669) since home assistant installs
+            # execinfo-dev when building wheels. The setup.py does not have an option for
+            # adding a single LDFLAG so copy all relevant linux flags here (as of 1.43.0)
+            echo "GRPC_PYTHON_LDFLAGS=\"-lpthread -Wl,-wrap,memcpy -static-libgcc -lexecinfo\""
           ) > .env_file
 
       - name: Upload env_file