build-llvm: Bump to LLVM 17.0.0 RC1

Relevant changes since 16.0.6 are:
- Improve Address Sanitizer on i686 mingw
- Improve handling of X86 Intel assembly syntax
- Fix using std::wcout/wcin/wcerr with streams configured in wide mode
- Improve handling of the .arch and .arch_extension assembly directives
  on aarch64
- Support the --temp-prefix (ignored) and --no-leading-underscore
  options in llvm-dlltool
- Make lld warn about too narrow pseudo relocations, simplifying finding
  issues that otherwise only show up at runtime
- Improved the tests, making compiler-rt, libcxxabi and libunwind tests
  pass in mingw configurations

build-llvm.sh

@@ -16,7 +16,7 @@
 
 set -e
 
-: ${LLVM_VERSION:=llvmorg-16.0.6}
+: ${LLVM_VERSION:=llvmorg-17.0.0-rc1}
 ASSERTS=OFF
 unset HOST
 BUILDDIR="build"