Add support for LLVM 15

[thedataking]

clang::StringLiteral::StringKind::Ascii was renamed to clang::StringLiteral::StringKind::Ordinary. Add release keys and update build_translator.py. Closes #676.

[chrysn]

Unrelated trouble with earlier Debian versions that's not this PR's fault

Testers on not-perfectly-recent Debian beware that the change to LLVM 15 that requires this (the StringLiteral::StringKind renaming) came in quite late in the LLVM release process. Users of Debian experimental will find that the new version will not build on some versions of llvm-15-dev, but that the current master does work. This is no fault of this PR, but of the Debian package claiming something to be -15 when it doesn't have all of -15's changes (but to be fair, it is an experimental pre-release, and needs to be opted in to).

With the very latest experimental release (llvm-15 1:15.0.1-1~exp2 from Debian, including mlir-15-tools, and a bunch of packages the build process will conveniently ask for), this passes compilation, but fails at link time:

  = note: /usr/bin/ld: /usr/lib/llvm-15/lib/libclangSema.a(SemaRISCVVectorLookup.cpp.o): in function `clang::CreateRISCVIntrinsicManager(clang::Sema&)':
          (.text._ZN5clang27CreateRISCVIntrinsicManagerERNS_4SemaE+0x1b8): undefined reference to `clang::RISCV::RVVIntrinsic::computeBuiltinTypes(llvm::ArrayRef<clang::RISCV::PrototypeDescriptor>, bool, bool, bool, unsigned int)'
          /usr/bin/ld: (.text._ZN5clang27CreateRISCVIntrinsicManagerERNS_4SemaE+0x1f9): undefined reference to `clang::RISCV::RVVIntrinsic::computeBuiltinTypes(llvm::ArrayRef<clang::RISCV::PrototypeDescriptor>, bool, bool, bool, unsigned int)'

I think this would be resolved by not only linking in libclangSema.a but also libclangSupport.a, but I don't know where that's stated (yet?).

[chrysn]

... and I have a patch:

diff --git a/c2rust-ast-exporter/build.rs b/c2rust-ast-exporter/build.rs
index 4dd17e88..22581b66 100644
--- a/c2rust-ast-exporter/build.rs
+++ b/c2rust-ast-exporter/build.rs
@@ -172,6 +172,7 @@ fn build_native(llvm_info: &LLVMInfo) {
             "clangParse",
             "clangSerialization",
             "clangSema",
+            "clangSupport",
             "clangEdit",
             "clangAnalysis",
             "clangDriver",

(Can't test whether that needs version sensing to decide whether or not to add that, as I don't want to shuffle around all my local packages once more -- I trust CI would give clear indications here)

[edit: With that patch, this branch not only builds but passes all my application tests so far, except where there are other open PRs]

[thedataking]

Thanks @chrysn, I've incorporated your suggestion. Let me know if you hit any other issues.

[kkysen]

I think llvm_major_ver() -> int would be better, and do the >= at call site. It's much easier to read and more flexible, and test_ver isn't otherwise used in llvm_major_ver_ge.

[kkysen]

I would put this inline as something like if llvm_info.llvm_major_version >= 15 { "clangSupport" } else { "" } and then filter out "". It's much cleaner, easier to understand the order of libraries, and more extensible if we need to add conditional libraries where order matters.

[kkysen]

Do we not need to do a similar libclang_path.exists() check for macOS like we do for linux?