build-llvm: Bump to LLVM 17.0.2

This contains a few bugfixes for mingw use cases:
- LLD in 17.0.1 and the earlier 17.x release candidates looked up
  libraries (including libraries named as a relative path) preferring
  to search in toolchain relative paths over first testing from the
  current directory. In some cases, this could cause cryptic build
  failures; see https://github.com/llvm/llvm-project/issues/67779.
- Options that only are relevant for linking, like -mwindows, used
  to be accepted (but produce a warning) if used in a compilation-only
  job. In the earlier 17.x releases/RCs, such warnings caused an
  error instead; see https://github.com/llvm/llvm-project/issues/64464
  and https://github.com/mstorsjo/llvm-mingw/issues/371.

build-llvm.sh

@@ -16,7 +16,7 @@
 
 set -e
 
-: ${LLVM_VERSION:=llvmorg-17.0.1}
+: ${LLVM_VERSION:=llvmorg-17.0.2}
 ASSERTS=OFF
 unset HOST
 BUILDDIR="build"