Set current astbuilder for reflection API (#7488)

With the test code in the issue, a crash was observed inside Slang::DeclRefBase::getParent()
while accessing the astbuilder which was nullptr. This PR adds a fix for that.

For the test code in the issue, we now get:
================================================
    found Outer<float>::Inner: true
    found foo function: true
    function name: "foo"
    parameter count: 1
    attempting getParameterByIndex(0): true
    getParameterByIndex(0) succeeded: true
    parameter name: "param"
    parameter type: "float"
================================================
Fixes #6546

0 files changed, 0 insertions, 0 deletions