[clangd] Avoid clangd crash with -fsycl flag

[rafbiels]

Add four extra option resets in disableUnsupportedOptions when parsing SYCL code. All four are needed to make clangd happily parse code when -fsycl is specified in compile commands. Without each of them, the following happens:

• without SYCLIsDevice=false: crash on !nullptr assert
• without DeclareSPIRVBuiltins=false: crash on !nullptr assert
• without SYCLUnnamedLambda=false: ref_non_value error, 'T' does not refer to a value
• without Triple=HostTriple: pp_file_not_found error, 'gnu/stubs-32.h' file not found

Fixes #11088 and clangd/clangd#1097

Also add a LIT test which parses the following code:

#include <sycl/sycl.hpp>
sycl::queue q{};

and checks symbolInfo for the symbol q against a reference.

[premanandrao]

Not sure who the reviewers for this should be.

[elizabethandrews]

Not sure who the reviewers for this should be.

Yea me neither. @bader the FE team does not have experience with clangd. Who should the code owners be for this PR?

[bader]

Not sure who the reviewers for this should be.

Yea me neither. @bader the FE team does not have experience with clangd. Who should the code owners be for this PR?

I don't know anyone who works with clangd on this project. Considering that this is a clang tool @intel/dpcpp-cfe-reviewers is the best option we have. Based on the changes I guess @intel/dpcpp-clang-driver-reviewers team might be able to help, but I don't know if clangd shares any logic with the clang driver.

[rafbiels]

@intel/dpcpp-cfe-reviewers I would appreciate any further review comments or launching the tests if this version looks OK.

[premanandrao]

LGTM