Allow installing dir from build dir

mesonbuild/backend/backends.py

@@ -1335,7 +1335,11 @@ class Backend:
 
     def generate_subdir_install(self, d):
         for sd in self.build.get_install_subdirs():
-            src_dir = os.path.join(self.environment.get_source_dir(),
+            if sd.from_source_dir:
+                from_dir = self.environment.get_source_dir()
+            else:
+                from_dir = self.environment.get_build_dir()
+            src_dir = os.path.join(from_dir,
                                    sd.source_subdir,
                                    sd.installable_subdir).rstrip('/')
             dst_dir = os.path.join(self.environment.get_prefix(),

mesonbuild/interpreter.py

@@ -741,7 +741,8 @@ class DataHolder(InterpreterObject, ObjectHolder):
         return self.held_object.install_dir
 
 class InstallDir(InterpreterObject):
-    def __init__(self, src_subdir, inst_subdir, install_dir, install_mode, exclude, strip_directory):
+    def __init__(self, src_subdir, inst_subdir, install_dir, install_mode,
+                 exclude, strip_directory, from_source_dir=True):
         InterpreterObject.__init__(self)
         self.source_subdir = src_subdir
         self.installable_subdir = inst_subdir
@@ -749,6 +750,7 @@ class InstallDir(InterpreterObject):
         self.install_mode = install_mode
         self.exclude = exclude
         self.strip_directory = strip_directory
+        self.from_source_dir = from_source_dir
 
 class Man(InterpreterObject):