Fix llama runner cmake for android (#2673)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/2673

This diff fixes:
1. Make sure we buidl static variant lib for ANDROID
2. Compile libexecutorch as whole-archive to not drop prim ops registration
3. gflags and executorch's *-config.cmake wasn't found so explicitly set the
directory path.
4. Add log as dep for android as cpuinfo depends on it.
ghstack-source-id: 220378206
exported-using-ghexport

Pre-existing lint failures
bypass-github-export-checks
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Reviewed By: digantdesai, mcr229

Differential Revision: D55344017

fbshipit-source-id: 6c2158db60d22c8441584ea5a9fbad1087aa621c