Support more linker versions in Makefile

Changes the way LLVM & Clang object files are detected & extracted in
the default Makefile to handle a wider variety of linker `-t` output formats.

Makefile

@@ -108,7 +108,7 @@ LLVM_LIBRARY_FLAGS += -lclangFrontend -lclangDriver \
                       -lclangAnalysis \
                       -lclangEdit -lclangAST -lclangLex -lclangBasic
 
-CLANG_AST_MATCHERS = "80 90 100 110 111"
+CLANG_AST_MATCHERS = "80 90 100 110 111 120"
 ifneq (,$(findstring $(LLVM_VERSION),$(CLANG_AST_MATCHERS)))
 LLVM_LIBRARY_FLAGS += -lclangASTMatchers
 endif
@@ -229,9 +229,22 @@ release/include/terra/%.h:  $(LUAJIT_INCLUDE)/%.h $(LUAJIT_LIB)
 
 build/llvm_objects/llvm_list:    $(addprefix build/, $(LIBOBJS) $(EXEOBJS))
 	mkdir -p build/llvm_objects/luajit
-	$(CXX) -o /dev/null $(addprefix build/, $(LIBOBJS) $(EXEOBJS)) $(LLVM_LIBRARY_FLAGS) $(SUPPORT_LIBRARY_FLAGS) $(LFLAGS) -Wl,-t 2>&1 | egrep "lib(LLVM|clang)"  > build/llvm_objects/llvm_list
-	# extract needed LLVM objects based on a dummy linker invocation
-	< build/llvm_objects/llvm_list $(LUAJIT) src/unpacklibraries.lua build/llvm_objects
+	# Extract needed LLVM objects based on a dummy linker invocation:
+	# - Older linkers output '(libName.a)object.o' per line, 
+	# - Newer versions output just 'libName.a', unless -t is passed twice.
+	# grep & uniq are used to get just the paths to the static libraries needed.
+	$(CXX) -o /dev/null $(addprefix build/, $(LIBOBJS) $(EXEOBJS)) $(LLVM_LIBRARY_FLAGS) $(SUPPORT_LIBRARY_FLAGS) $(LFLAGS) -Wl,-t 2>&1 \
+		| egrep -o "[^()]*lib(LLVM|clang|Polly).*\.a" \
+		| uniq \
+		> build/llvm_objects/llvm_list
+	# Extract all the static libraries to build/llvm_objects/*
+	cd build/llvm_objects; for lib in $$(cat llvm_list); do \
+		DIR=$$(basename $$lib .a); \
+		mkdir -p $$DIR; \
+		cd $$DIR; \
+		ar x $$lib; \
+		cd ..; \
+	done
 	# include all luajit objects, since the entire lua interface is used in terra