glcpp: Fix support for nested #ifdef and nested #ifndef

Previously, if the outer #ifdef/#ifndef evaluated to false, the inner
directive would not be parsed correctly, (the identifier as the subject
of the #ifdef/#ifndef would inadvertently be skipped along with the other
content correctly being skipped).

We fix this by setting the lexing_if state in each case here.

We also add a new test to the test suite to ensure that this case is tested.

1 files changed, 41 insertions, 0 deletions

diff --git a/src/glsl/glcpp/tests/067-nested-ifdef-ifndef.c.expected b/src/glsl/glcpp/tests/067-nested-ifdef-ifndef.c.expected
new file mode 100644
index 0000000000..3340daaa1f
--- /dev/null
+++ b/src/glsl/glcpp/tests/067-nested-ifdef-ifndef.c.expected
@@ -0,0 +1,41 @@
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