Turn off parallel builds in protobuf conformance.

This works for in the ObjC build script, but builds a slightly larger set of
things so it must be luck there. leave the build serial just to be safe.

Author: thomasvl

.github/workflows/build.yml

@@ -79,7 +79,7 @@ jobs:
         ./configure
         NUM_CPUS=$(getconf _NPROCESSORS_ONLN)
         make -C ./src -j "${NUM_CPUS}" protoc
-        make -C ./conformance -j "${NUM_CPUS}" conformance-test-runner
+        make -C ./conformance conformance-test-runner
     - name: Test plugin
       working-directory: main
       run: make test-plugin PROTOC=../protobuf/src/protoc

.github/workflows/regular_conformance.yml

@@ -75,7 +75,7 @@ jobs:
         ./configure
         NUM_CPUS=$(getconf _NPROCESSORS_ONLN)
         make -C ./src -j "${NUM_CPUS}" protoc
-        make -C ./conformance -j "${NUM_CPUS}" conformance-test-runner
+        make -C ./conformance conformance-test-runner
     - name: Test conformance
       working-directory: main
       run: make test-conformance