mparser: store subdir in ternary node

Ternaries don't really need subdirs, but they can be passed into
functions that expect the type they're provided to have a
subdir. Provide it to fulful the interface.

Fixes mesonbuild#5003
Fixes mesonbuild#3690
Fixes mesonbuild#2404

mesonbuild/mparser.py

@@ -405,7 +405,8 @@ def __init__(self, lineno, colno, condition, block):
  self.block = block
 
 class TernaryNode(BaseNode):
- def __init__(self, lineno, colno, condition, trueblock, falseblock):
+ def __init__(self, subdir, lineno, colno, condition, trueblock, falseblock):
+ self.subdir = subdir
  self.lineno = lineno
  self.colno = colno
  self.condition = condition
@@ -540,7 +541,7 @@ def e1(self):
  self.expect('colon')
  falseblock = self.e1()
  self.in_ternary = False
- return TernaryNode(left.lineno, left.colno, left, trueblock, falseblock)
+ return TernaryNode(left.subdir, left.lineno, left.colno, left, trueblock, falseblock)
  return left
 
  def e2(self):