[builder][standalone-build-x86_64] Batch build commits

[kwk]

Summary

This enables batch builds as a last resort to make builds faster regarding https://llvm.org/docs/HowToAddABuilder.html#best-practices-for-configuring-a-fast-builder

[nikic]

LGTM

[nikic]

I'd recommend also adding -DLLVM_CCACHE_BUILD=ON to the cmake invocations in https://github.com/llvm/llvm-zorg/blob/main/zorg/buildbot/builders/annotated/standalone-build.sh. This should significantly reduce average build time.

buildbot/osuosl/master/config/builders.py

'factory' : UnifiedTreeBuilder.getCmakeWithNinjaBuildFactory(
              'CC': 'clang',
              'CXX': 'clang++',
              'LD': 'lld',
          })},
 
     # Standalone builder
     {'name' : "standalone-build-x86_64",
     'tags'  : ["clang"],
-    'collapseRequests': False,
+    'collapseRequests': True,
     'workernames':["standalone-build-x86_64"],
     'builddir':"standalone-build-x86_64",
     'factory' : AnnotatedBuilder.getAnnotatedBuildFactory(
                     script="standalone-build.sh",
                     checkout_llvm_sources=False,
                     script_interpreter=None)},
 
     ## CSKY check-all + test-suite in soft-float