Remove all autotools usage (#10132)

* Bazelfying conformance tests

Adding infrastructure to "Bazelify" languages other than Java and C++

* Delete benchmarks for languages supported by other repositories

* Bazelfying benchmark tests

* Bazelfying python

Use upb's system python rule instead of branching tensorflow

* Bazelfying Ruby

* Bazelfying C#

* Bazelfying Objective-c

* Bazelfying Kokoro mac builds

* Bazelfying Kokoro linux builds

* Deleting all deprecated files from autotools cleanup

This boils down to Makefile.am and tests.sh and all of their remaining references

* Cleanup after PR reorganizing

- Enable 32 bit tests
- Move conformance tests back
- Use select statements to select alternate runtimes
- Add internal prefixes to proto library macros

* Updating READMEs to use bazel instead of autotools.

* Bazelfying Kokoro release builds

* First round of review fixes

* Second round of review fixes

* Third round of review fixes

* Filtering out conformance tests from Bazel on Windows (b/241484899)

* Add version metadata that was previously scraped from configure.ac

* fixing typo from previous fix

* Adding ruby version tests

* Bumping pinned upb version, and adding tests to python CI
diff --git a/objectivec/DevTools/compile_testing_protos.sh b/objectivec/DevTools/compile_testing_protos.sh
index 69c32f9..eb43cae 100755
--- a/objectivec/DevTools/compile_testing_protos.sh
+++ b/objectivec/DevTools/compile_testing_protos.sh
@@ -89,7 +89,8 @@
 # Move to the top of the protobuf directories and ensure there is a protoc
 # binary to use.
 cd "${SRCROOT}/.."
-[[ -x src/protoc ]] || \
+readonly PROTOC="bazel-bin/protoc"
+[[ -x $PROTOC ]] || \
   die "Could not find the protoc binary; make sure you have built it (objectivec/DevTools/full_mac_build.sh -h)."
 
 # -----------------------------------------------------------------------------
@@ -120,7 +121,7 @@
   readonly NewestInput=$(find \
      src/google/protobuf/*.proto \
      objectivec/Tests/*.proto \
-     src/.libs src/*.la src/protoc \
+     src/.libs src/*.la $PROTOC \
      objectivec/DevTools/compile_testing_protos.sh \
         -type f -print0 \
         | xargs -0 stat -f "%m %N" \
@@ -152,7 +153,7 @@
 # -----------------------------------------------------------------------------
 # Helper to invoke protoc
 compile_protos() {
-  src/protoc                                   \
+  $PROTOC                                  \
     --objc_out="${OUTPUT_DIR}/google/protobuf" \
     --proto_path=src/google/protobuf/          \
     --proto_path=src                           \