Merge bitcoin/bitcoin#32731: depends: Build qt package for FreeBSD hosts

173394d951 depends: Build `qt` package for FreeBSD hosts (Hennadii Stepanov)

Pull request description:

  This PR continues the work started in https://github.com/bitcoin/bitcoin/pull/23948.

  Here is an excerpt from the log:
  ```
  $ ./build/bin/bitcoin-qt -printtoconsole
  2025-06-12T01:06:56Z Bitcoin Core version v29.99.0-15de25ba2a28 (release build)
  2025-06-12T01:06:56Z Qt 6.7.3 (static), plugin=xcb
  2025-06-12T01:06:56Z Static plugins:
  2025-06-12T01:06:56Z  QMinimalIntegrationPlugin, version 395008
  2025-06-12T01:06:56Z  QXcbIntegrationPlugin, version 395008
  2025-06-12T01:06:56Z Style: fusion / QFusionStyle
  2025-06-12T01:06:56Z System: FreeBSD 14.3-RELEASE, x86_64-little_endian-lp64
  ```

  And here are the screenshots:

  ![image](https://github.com/user-attachments/assets/acf3fefc-ee3f-41cb-ab9a-3bc4d49c7054)

  ![image](https://github.com/user-attachments/assets/6280303f-9c7b-445d-8428-172ea998343d)

ACKs for top commit:
  vasild:
    ACK 173394d951

Tree-SHA512: 42a0bd11e4ef1a23efcfe6c4ab179dc667a076e65060891ce8358b3fe78de4e3ea33f975387d4236cc2ac620e2935b0a29c278065a47f038c66658106bf36755

depends/toolchain.cmake.in

@@ -117,7 +117,7 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Darwin" AND NOT CMAKE_HOST_APPLE)
 endif()
 
 
-if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+if(CMAKE_SYSTEM_NAME MATCHES "^(Linux|FreeBSD)$")
   # Customize pkg-config behavior for finding dependencies
   # of the xcb QPA platform plugin:
   # 1. Restrict search paths to the depends.