This ensures that solution files have correctly numbered icons in
Windows Explorer.

Previously, when saving a temporary project, two native dialogs would be
created. The first was very short-lived, as it was automatically
dismissed by the second dialog. On older macOS versions, this appeared
to work correctly (the first dialog was so short-lived that it did not
appear to the user). However, on macOS 12.0, the second dialog fails to
display altogether.

Displaying two file chooser dialogs feels like a programming error, so
the code has been reorganised a bit to avoid this case.

By default, x86_64 binaries are not signed, but arm64 binaries are. When
building universal binaries, it was possible to end up with a final
artefact that contains an unsigned x86_64 image, but a signed arm64
image. In some cases, this could cause issues in subsequent codesign
invocations.

When the result of find_if() is only compared to the container's end(),
the operation can normally be expressed more concisely using any_of(),
all_of(), or none_of().

5f7ad995af introduced an issue where the
string of external libraries would be escaped in one go. This is
incorrect, because only the individual paths should be escaped. The
semicolons separating each path should not be escaped.

Without the BOM, VS assumes UTF-8 strings (subproject file names etc.)
are ansi-encoded.