Use makedirs instead of mkdir. Closes #247.

interpreter.py

@@ -1540,7 +1540,7 @@ class Interpreter():
         self.visited_subdirs[subdir] = True
         self.subdir = subdir
         try:
-            os.mkdir(os.path.join(self.environment.build_dir, subdir))
+            os.makedirs(os.path.join(self.environment.build_dir, subdir))
         except FileExistsError:
             pass
         buildfilename = os.path.join(self.subdir, environment.build_filename)

test cases/common/92 skip subdir/meson.build

@@ -0,0 +1,3 @@
+project('foo', 'c')
+
+subdir('subdir1/subdir2')

test cases/common/92 skip subdir/subdir1/meson.build

@@ -0,0 +1 @@
+error('This should not be called.')

test cases/common/92 skip subdir/subdir1/subdir2/meson.build

@@ -0,0 +1 @@
+message('I\'m in subdir subdir.')