CMake: Make lupdate/lrelease callable when building Qt

We'll use the CMake translation API in a subsequent commit.  In
preparation of that, we must ensure that lupdate/lrelease can be called
when building Qt with examples.

Prepare the commands with _qt_internal_wrap_tool_command(), which
ensures that the Qt DLLs are in PATH when running on Windows by
prepending the actual command with a batch file.

With CMake >= 3.20 and Ninja Multi-Config, add_custom_target might not
add the correct dependency to lupdate/lrelease if the $<TARGET_FILE>
generator expression is not the first argument after COMMAND.  We need
$<TARGET_FILE> to be evaluated in the "command config", however it's
evaluated in the "output config".  According to the Ninja Multi-Config
documentation of CMake, $<TARGET_FILE> should be evaluated in the
"command config", since the OUTPUT here is always "a path that is common
to more than one configuration".  See upstream issue #22855.

We force a "command config" dependency to lupdate (and lrelease) by
adding an explicit "DEPENDS Qt6::lupdate".  That CMake here chooses the
"command config" dependency is what we deem as the correct behavior,
which won't change after #22855 is fixed.

Change-Id: I9dfbd5e903fc3b7306402a4eb7feef59e9c83ec2
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

0 files changed, 0 insertions, 0 deletions