meson: extract the version directly from ./VERSION without subprocesses

With the new minimum meson_version, it is possible to retrieve the
project version from a file by passing a files() output directly to the
version argument. It is no longer necessary to call run_command with
various arguments to configure its behavior, nor depend on a system
/usr/bin/cat (which admittedly does exist on non-Windows systems).

And meson will also treat the VERSION file as a build input, and
reconfigure the build if it changes -- meaning that the built binaries
are updated to have the correct version number (configure_file,
PACKAGE_VERSION, etc).

Signed-off-by: Eli Schwartz <eschwartz@gentoo.org>

meson.build

@@ -1,5 +1,5 @@
 project('zoitechat', 'c',
-  version: run_command('cat', 'VERSION', check: true).stdout().strip(),
+  version: files('VERSION'),
   meson_version: '>= 0.59.0',
   default_options: [
     'c_std=c17',