auto merge of #6713 : alexcrichton/rust/llvm-upgrades, r=catamorphism

This includes some of @brson's patches, plus one of mine. A multithreaded-llvm is necessary for running `rusti` tests in parallel, and in general is a good idea for running `rustc` in parallel.

Author: bors

configure

@@ -818,8 +818,7 @@ do
 
         # Disable unused LLVM features
         LLVM_OPTS="$LLVM_DBG_OPTS --disable-docs \
-                   --enable-bindings=none --disable-threads \
-                   --disable-pthreads"
+                   --enable-bindings=none"
 
         if [ "$CFG_C_COMPILER" = "clang" ]
         then

mk/llvm.mk

@@ -14,7 +14,9 @@ LLVM_DEPS := $(S)/.gitmodules
 else
 
 # This is just a rough approximation of LLVM deps
-LLVM_DEPS=$(call rwildcard,$(CFG_LLVM_SRC_DIR),*cpp *hpp)
+LLVM_DEPS_SRC=$(call rwildcard,$(CFG_LLVM_SRC_DIR)/src,*cpp *hpp)
+LLVM_DEPS_INC=$(call rwildcard,$(CFG_LLVM_SRC_DIR)/include,*cpp *hpp)
+LLVM_DEPS=$(LLVM_DEPS_SRC) $(LLVM_DEPS_INC)
 endif
 
 define DEF_LLVM_RULES