Identify modules ready to be converted to Soong

The output will be in the `m dist` results as soong_to_convert.txt, or
can be built using:

  $ m $OUT/soong_to_convert.txt

The output is a list of modules that are probably ready to convert to
Soong:

  # Blocked on Module (potential problems)
           283 libEGL (srcs_dotarm)
           246 libicuuc (dotdot_incs dotdot_srcs)
           221 libspeexresampler
           215 libcamera_metadata
               ...
             0 zram-perf (dotdot_incs)

The number at the beginning of the line shows how many native modules
depend on that module.

All of their dependencies have been satisfied, and any potential
problems that Make can detect are listed in parenthesis after the
module:

  dotdot_srcs: LOCAL_SRC_FILES contains paths outside $(LOCAL_PATH)
  dotdot_incs: LOCAL_C_INCLUDES contains paths include '..'
  srcs_dotarm: LOCAL_SRC_FILES contains source files like <...>.c.arm
  aidl: LOCAL_SRC_FILES contains .aidl sources
  dbus: LOCAL_SRC_FILES contains .dbus-xml sources
  objc: LOCAL_SRC_FILES contains Objective-C sources
  proto: LOCAL_SRC_FILES contains .proto sources
  rs: LOCAL_SRC_FILES contains renderscript sources
  vts: LOCAL_SRC_FILES contains .vts sources

Not all problems can be discovered, but this is a starting point.

Change-Id: I45674fe93fd267d4d1fb0bc3bc9aa025e20c5ac6