Add a note to msvc readme re building Qt for Bitcoin Core. #29048

Updated the msvc readme with a note about avoiding path too long errors when building Qt with Bitcoin Core.

Would have saved me half an hour if I'd remembered this from the last time I did the build.

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~ACK a9b9fb2eeedbd9094d74f8f429622ba7d600dda3~, the tip is correct and useful.

However, it won't be needed after migration to CMake as vcpkg's Qt package will be used then.

@sipsorcery

There is a linter error in CI:

File "build_msvc/README.md" has permission 755 (executable) and is thus expected to contain a shebang '#!'. Add shebang or do "chmod 644 build_msvc/README.md" to make it non-executable.

@sipsorcery

There is a linter error in CI:

Even after I manually checked for whitespace violations on that single line addition :(.

Although it does seem like the linter culprit may be elsewhere? Or, am I missing something?

src/test/fuzz/package_eval.cpp:214: non-existant ==> non-existent
src/test/span_tests.cpp:56: memeber ==> member
^ Warning: codespell identified likely spelling errors. Any false positives? Add them to the list of ignored words in test/lint/spelling.ignore-words.txt
File "build_msvc/README.md" has permission 755 (executable) and is thus expected to contain a shebang '#!'. Add shebang or do "chmod 644 build_msvc/README.md" to make it non-executable.
ERROR: There were 1 failed tests in the lint-files.py lint test. Please resolve the above errors.
^---- failure generated from lint-files.py

Or, am I missing something?

Just rewording the linter:

The problem is:

$ stat build_msvc/README.md 
  File: build_msvc/README.md
  Size: 5650      	Blocks: 16         IO Block: 4096   regular file
Device: 10303h/66307d	Inode: 14949723    Links: 1
Access: (0755/-rwxr-xr-x)  Uid: ( 1001/ hebasto)   Gid: ( 1001/ hebasto)
Access: 2023-12-10 15:34:07.780145234 +0000
Modify: 2023-12-10 15:34:06.520175365 +0000
Change: 2023-12-10 15:34:06.520175365 +0000
 Birth: 2023-12-10 15:34:06.520175365 +0000

The fix is:

$ chmod 644 build_msvc/README.md

(the POSIX environment is assumed)

@sipsorcery

We make such changes in a single commit usually :)

Mind squashing your commits?

ACK d08e820abf5da2be09b8a84b5bd3450d1a55a039.

ACK d08e820abf5da2be09b8a84b5bd3450d1a55a039