Retain comments from linker.config.txt.

They were removed in https://r.android.com/1450478.

Also reformatted the JSON file for consistency with manifest-art.json.

Test: `m com.android.art` and check that
  out/soong/.intermediates/art/build/apex/art-linker-config/android_x86/linker.config.pb
  reflects linker.config.json.
Bug: 169634881
Change-Id: I1afc3c6fa96caf5084e2b428e3b70a981fb7e12e
1 file changed