[gn] Add explicit deps on TargetParser

This diff was generated by the following script:

    #!/usr/bin/env python3
    import os, subprocess
    r = subprocess.run('git show --pretty='' --name-only f09cf34d'.split(),
                       stdout=subprocess.PIPE, text=True)
    for line in r.stdout.splitlines():
      if not line.endswith('CMakeLists.txt'): continue
      gn = 'llvm/utils/gn/secondary/' + os.path.dirname(line) + '/BUILD.gn'
      if not os.path.exists(gn): continue
      with open(gn) as f:
        contents = f.read()
      if contents.count('"//llvm/lib/Support",') == 1:
        contents = contents.replace(
            '"//llvm/lib/Support",',
            '"//llvm/lib/Support", "//llvm/lib/TargetParser",')
      elif contents.count(' deps = [') == 1:
        contents = contents.replace(
            ' deps = [',
            ' deps = [ "//llvm/lib/TargetParser",')
      else:
        print('needs manual fixup:', gn)
        continue
      with open(gn, 'w') as f:
        f.write(contents)

I then manually fixed up the BUILD.gn files for Support (should not depend on
TargetParser) and TargetParser (should depend on Support) and ran `gn format`
on all touched files.