mingw-builds: detect conflict with mingw-w64

[ericLemanissier]

Specify library name and version: mingw-builds/*

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• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[conan-center-bot]

All green in build 1 (3de8d92507e94b55c229d8f858d3567df7050465):

• mingw-builds/8.1@:
  All packages built successfully! (All logs)

• mingw-builds/11.2.0@:
  All packages built successfully! (All logs)