lang/rust: bump PORT_LLVM minimum version to 16

Source: rust-lang/rust@7de6d04

Author: vishwin

lang/rust/Makefile

@@ -60,7 +60,7 @@ DOCS_VARS=		_RUST_BUILD_DOCS=true \
 			_RUST_TOOLS+=rustdoc
 DOCS_VARS_OFF=		_RUST_BUILD_DOCS=false
 GDB_RUN_DEPENDS=	${LOCALBASE}/bin/gdb:devel/gdb
-PORT_LLVM_USES=		llvm:min=15,lib,noexport
+PORT_LLVM_USES=		llvm:min=16,lib,noexport
 PORT_LLVM_MAKE_ENV=	RUSTFLAGS="-Lnative=${LOCALBASE}/lib"
 SOURCES_VARS=		_COMPONENTS+=rust-src-${_PACKAGE_VERS} \
 			_RUST_TOOLS+=src