meson: same option for meson -Dcheck-update=false as previous commit.

Separate commit for easy cherry-picking.

meson.build

@@ -1113,6 +1113,8 @@ else
   conf.set_quoted('GIMP_BUILD_PLATFORM_FAMILY', 'other')
 endif
 
+conf.set('CHECK_UPDATE', get_option('check-update'))
+
 # Default ICC directory #
 
 # This is necessary because some Unix systems may have a different
@@ -1781,6 +1783,7 @@ final_message = [
 '''  gimp-console:        @0@'''.format(enable_console_bin),
 '',
 '''Optional Features:''',
+'''  Check updates at startup:  @0@'''.format(get_option('check-update')),
 '''  Language selection:        @0@'''.format(isocodes.found()),
 '''  Vector icons:              @0@'''.format(have_vector_icons),
 '''  Dr. Mingw (Win32):         @0@'''.format(drmingw.found()),

meson_options.txt

@@ -14,6 +14,8 @@ option('shmem-type',        type: 'combo',   value: 'auto', description: 'Shared
 
 option('build-id',          type: 'string',  value: 'unknown', description: 'Unique string used to define your build')
 option('revision',          type: 'integer', value: 0,    description: 'Revision increment for a same build/version/platform')
+option('check-update',      type: 'boolean', value: true, description: 'GIMP will look up new version availability on startup')
+
 option('bug-report-url',    type: 'string',  value: '',   description: 'URL used by the debug dialog to report bugs')
 option('gimpdir',           type: 'string',  value: '',   description: 'Change default gimpdir from ~/.config/GIMP/2.9 to ~/.config/DIR/2.9 (if relative), or to DIR (if absolute)')
 option('icc-directory',     type: 'string',  value: '',   description: 'Path to default color profiles for this system')