Attempting to detect windows to add the option you need.

sfmldemo/meson.build

@@ -1,14 +1,20 @@
 project('sfmldemo', 'cpp',
-  default_options: [
-    'default_library=static',
-    'cpp_std=c++17',
-    ])
+  default_options: ['cpp_std=c++17'])
 
-sfml_dep = dependency('sfml')
-imgui_dep = dependency('imgui-sfml')
-fmt_dep = dependency('fmt')
+if host_machine.system() == 'windows'
+  defaults = ['library_default=static']
+else
+  defaults = []
+endif
+
+dependencies = [
+  dependency('sfml'),
+  dependency('imgui-sfml'),
+  dependency('fmt'),
+]
 
 executable('sfmldemo', 'main.cpp',
   win_subsystem: 'windows',
   cpp_args: '-DFMT_HEADER_ONLY',
-  dependencies: [sfml_dep, imgui_dep, fmt_dep])
+  override_options: defaults,
+  dependencies: dependencies)