build-llvm: Bump to LLVM 21.1.4

This version fixes catching pointer data types by reference in C++.

This version also fixes throwing C++ exceptions on aarch64 with
a debugger attached to the process.

Finally, this version fixes delayimport calling of C++ methods that
return structs on aarch64.

build-llvm.sh

@@ -16,7 +16,7 @@
 
 set -e
 
-: ${LLVM_VERSION:=llvmorg-21.1.3}
+: ${LLVM_VERSION:=llvmorg-21.1.4}
 ASSERTS=OFF
 unset HOST
 BUILDDIR="build"