Look for LLVM 15 in makefile

Makefile

@@ -10,7 +10,7 @@ LLD_SRC ?= $(LLVM_PROJECTDIR)/lld
 
 # Try to autodetect LLVM build tools.
 # Versions are listed here in descending priority order.
-LLVM_VERSIONS = 14 13 12 11
+LLVM_VERSIONS = 15 14 13 12 11
 errifempty = $(if $(1),$(1),$(error $(2)))
 detect = $(shell which $(call errifempty,$(firstword $(foreach p,$(2),$(shell command -v $(p) 2> /dev/null && echo $(p)))),failed to locate $(1) at any of: $(2)))
 toolSearchPathsVersion = $(1)-$(2)