Add LTO support of Clang/LLVM

We need to build LLVMgold.so and copy it to installation dir.

I think it deserves to be default, so I don't add an option to enable
this.

Author: wangpc-pp

Makefile.in

@@ -357,6 +357,8 @@ stamps/build-binutils-linux: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) $(PREPARATIO
 		$(CONFIGURE_HOST) \
 		--prefix=$(INSTALL_DIR) \
 		--with-sysroot=$(SYSROOT) \
+		--enable-gold \
+		--enable-plugins \
 		$(MULTILIB_FLAGS) \
 		@with_guile@ \
 		--disable-werror \
@@ -526,6 +528,8 @@ stamps/build-binutils-linux-native: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) stamp
 		--target=$(LINUX_TUPLE) \
 		$(CONFIGURE_HOST) \
 		--prefix=$(INSTALL_DIR)/native \
+		--enable-gold \
+		--enable-plugins \
 		$(MULTILIB_FLAGS) \
 		@with_guile@ \
 		--disable-werror \
@@ -583,6 +587,8 @@ stamps/build-binutils-newlib: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) $(PREPARATI
 		--target=$(NEWLIB_TUPLE) \
 		$(CONFIGURE_HOST) \
 		--prefix=$(INSTALL_DIR) \
+		--enable-gold \
+		--enable-plugins \
 		@with_guile@ \
 		--disable-werror \
 		$(BINUTILS_TARGET_FLAGS) \
@@ -770,6 +776,8 @@ stamps/build-binutils-musl: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) $(PREPARATION
 		$(CONFIGURE_HOST) \
 		--prefix=$(INSTALL_DIR) \
 		--with-sysroot=$(SYSROOT) \
+		--enable-gold \
+		--enable-plugins \
 		$(MULTILIB_FLAGS) \
 		@with_guile@ \
 		--disable-werror \
@@ -966,10 +974,12 @@ stamps/build-llvm-linux: $(LLVM_SRCDIR) $(LLVM_SRC_GIT) \
 	    -DDEFAULT_SYSROOT="../sysroot" \
 	    -DLLVM_RUNTIME_TARGETS=$(call make_tuple,$(XLEN),linux-gnu) \
 	    -DLLVM_INSTALL_TOOLCHAIN_ONLY=On \
+	    -DLLVM_BINUTILS_INCDIR=`find $(INSTALL_DIR) -name plugin-api.h | xargs dirname` \
 	    -DLLVM_PARALLEL_LINK_JOBS=4
 	$(MAKE) -C $(notdir $@)
 	$(MAKE) -C $(notdir $@) install
 	cp $(notdir $@)/lib/riscv$(XLEN)-unknown-linux-gnu/libc++* $(SYSROOT)/lib
+	cp $(notdir $@)/lib/LLVMgold.so  $(INSTALL_DIR)/lib
 	cd $(INSTALL_DIR)/bin && ln -s -f clang $(LINUX_TUPLE)-clang && ln -s -f clang++ $(LINUX_TUPLE)-clang++
 	mkdir -p $(dir $@) && touch $@
 
@@ -984,9 +994,11 @@ stamps/build-llvm-newlib: $(LLVM_SRCDIR) $(LLVM_SRC_GIT) stamps/build-gcc-newlib
 	    -DLLVM_ENABLE_PROJECTS="clang;lld" \
 	    -DLLVM_DEFAULT_TARGET_TRIPLE="$(NEWLIB_TUPLE)" \
 	    -DLLVM_INSTALL_TOOLCHAIN_ONLY=On \
+	    -DLLVM_BINUTILS_INCDIR=`find $(INSTALL_DIR) -name plugin-api.h | xargs dirname` \
 	    -DLLVM_PARALLEL_LINK_JOBS=4
 	$(MAKE) -C $(notdir $@)
 	$(MAKE) -C $(notdir $@) install
+	cp $(notdir $@)/lib/LLVMgold.so  $(INSTALL_DIR)/lib
 	cd $(INSTALL_DIR)/bin && ln -s -f clang $(NEWLIB_TUPLE)-clang && \
 	    ln -s -f clang++ $(NEWLIB_TUPLE)-clang++
 	mkdir -p $(dir $@) && touch $@