Add test case for "subproject:opt" in project()

This is regression test for #7573

test cases/common/90 default options/meson.build

@@ -4,6 +4,7 @@ project('default options', 'cpp', 'c', default_options : [
   'cpp_std=c++11',
   'cpp_eh=none',
   'warning_level=3',
+  'sub1:test_option=false',
   ])
 
 assert(get_option('buildtype') == 'debugoptimized', 'Build type default value wrong.')
@@ -28,3 +29,5 @@ assert(w_level == '3', 'warning level "' + w_level + '" instead of "3"')
 #   assert(not cc.compiles('int foobar;'), 'Default arg not used in test.')
 #   assert(cc.compiles('int foobar;', no_builtin_args : true), 'No_builtin did not disable builtins.')
 # endif
+
+subproject('sub1')

test cases/common/90 default options/subprojects/sub1/meson.build

@@ -0,0 +1,3 @@
+project('sub1')
+
+assert(get_option('test_option') == false)

test cases/common/90 default options/subprojects/sub1/meson_options.txt

@@ -0,0 +1 @@
+option('test_option', type : 'boolean', value : true, description : 'Test option. Superproject overrides default to "false"')