ExternalProgram: add cmd_array to complete the offfering

In case of python and especially in the case of pyInstaller
where the python command is meson.exe runpython, it should
not be full path to be used but cmd_array.

Fixing #13834

docs/yaml/objects/external_program.yaml

@@ -56,3 +56,8 @@ methods:
     ```meson
     run_command(find_program('foo'), 'arg1', 'arg2')
     ```
+
+- name: cmd_array
+  returns: list[str]
+  description: Returns an array containing the command(s) for the program.
+  since: 1.7.0

mesonbuild/interpreter/interpreterobjects.py

@@ -618,7 +618,8 @@ def __init__(self, ep: _EXTPROG, interpreter: 'Interpreter') -> None:
         self.methods.update({'found': self.found_method,
                              'path': self.path_method,
                              'version': self.version_method,
-                             'full_path': self.full_path_method})
+                             'full_path': self.full_path_method,
+                             'cmd_array': self.cmd_array_method})
 
     @noPosargs
     @noKwargs
@@ -645,6 +646,19 @@ def _full_path(self) -> str:
         assert path is not None
         return path
 
+    @noPosargs
+    @noKwargs
+    @FeatureNew('ExternalProgram.cmd_array', '1.6.1')
+    def cmd_array_method(self, args: T.List[TYPE_var], kwargs: TYPE_kwargs) -> T.List[str]:
+        return self._cmd_array()
+
+    def _cmd_array(self) -> T.List[str]:
+        if not self.found():
+            raise InterpreterException('Unable to get the path of a not-found external program')
+        cmd = self.held_object.get_command()
+        assert cmd is not None
+        return cmd
+
     @noPosargs
     @noKwargs
     @FeatureNew('ExternalProgram.version', '0.62.0')