build-llvm: Bump to llvmorg-14.0.0-rc2

Notable changes include:

- Default to DWARF 4 instead of 5 for the mingw target
- Fix the section name encoding in llvm-objcopy/llvm-strip, if the output
  binary has more than 10^6 bytes of string table

build-llvm.sh

@@ -16,7 +16,7 @@
 
 set -e
 
-: ${LLVM_VERSION:=llvmorg-14.0.0-rc1}
+: ${LLVM_VERSION:=llvmorg-14.0.0-rc2}
 ASSERTS=OFF
 unset HOST
 BUILDDIR="build"