Merge bitcoin/bitcoin#30580: doc: Add note about distro's g++-mingw-w64-x86-64-posix version

ed83974 doc: Add note about distro's g++-mingw-w64-x86-64-posix version (Hennadii Stepanov)

Pull request description:

  This PR stems from a requirement for the `g++` minimum supported version [being >= 11](bitcoin/bitcoin#29091):
  - https://packages.ubuntu.com/noble/g++-mingw-w64-x86-64-posix
  - https://packages.debian.org/bookworm/g++-mingw-w64-x86-64-posix

ACKs for top commit:
  m3dwards:
    ACK ed83974
  maflcko:
    review-only ACK ed83974

Tree-SHA512: a4c4d5239df5540b2dac922c2834c51337ec67310d596620bea02fe54334917e83da8954107c6a3fdd08143d1eac6a2cd4b0520ad023d7ccad8bcbdc4e03a7c0

Author: fanquake

doc/build-windows.md

@@ -13,6 +13,9 @@ Other options which may work, but which have not been extensively tested are (pl
 
 * On Windows, using a POSIX compatibility layer application such as [cygwin](https://www.cygwin.com/) or [msys2](https://www.msys2.org/).
 
+The instructions below work on Ubuntu and Debian. Make sure the distribution's `g++-mingw-w64-x86-64-posix`
+package meets the minimum required `g++` version specified in [dependencies.md](dependencies.md).
+
 Installing Windows Subsystem for Linux
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