Also add support for declare_dependency objects

mesonbuild/build.py

@@ -1150,7 +1150,7 @@ You probably should put it in link_with instead.''')
                 raise MesonException('File %s does not exist.' % f)
         self.pch[language] = pchlist
 
-    def add_include_dirs(self, args):
+    def add_include_dirs(self, args, set_is_system: typing.Optional[bool] = None):
         ids = []
         for a in args:
             # FIXME same hack, forcibly unpack from holder.
@@ -1159,6 +1159,8 @@ You probably should put it in link_with instead.''')
             if not isinstance(a, IncludeDirs):
                 raise InvalidArguments('Include directory to be added is not an include directory object.')
             ids.append(a)
+        if set_is_system is not None:
+            ids = [IncludeDirs(x.get_curdir(), x.get_incdirs(), set_is_system, x.get_extra_build_dirs()) for x in ids]
         self.include_dirs += ids
 
     def add_compiler_args(self, language, args):

test cases/common/226 is_system dependency/meson.build

@@ -18,3 +18,10 @@ assert(dep2.is_system() == true, 'is_system must be true when set')
 
 dep2_sys = dep2.as_system(false)
 assert(dep2_sys.is_system() == false, 'as_system must set is_system correctly')
+
+sp = subproject('subDep')
+sp_dep = sp.get_variable('subDep_dep')
+assert(sp_dep.is_system() == false, 'default is false')
+
+sp_dep_sys = sp_dep.as_system(true)
+assert(sp_dep_sys.is_system() == true, 'changing is_system works')

test cases/common/226 is_system dependency/subprojects/subDep/meson.build

@@ -0,0 +1,3 @@
+project('subDep', ['cpp'])
+
+subDep_dep = declare_dependency(compile_args : [])