rust: Reorder targets in makefile to make second expansion clearly.

.SECONDEXPANSION directive instructs targets AFTER it to expand twice.
According to GNU make manual, the special target .SECONDEXPANSION must
be defined before the first prerequisite list that makes use of this
feature.

For Rust's makefile, only sources from rust lib requires second
expansion. Move those targets to the end of makefile and tag only them
as .SECONDEXPANSION to prevent from error-prone bugs.

Signed-off-by: d0u9 <d0u9.su@outlook.com>

Author: d0u9

rust/Makefile

@@ -151,21 +151,11 @@ RUST_LIB_SRC ?= $(rustc_sysroot)/lib/rustlib/src/rust/library
 rust-analyzer:
 	$(Q)$(srctree)/scripts/generate_rust_analyzer.py $(srctree) $(objtree) $(RUST_LIB_SRC) $(objtree)/rust/bindings_generated.rs > $(objtree)/rust-project.json
 
-.SECONDEXPANSION:
-$(objtree)/rust/core.o: private skip_clippy = 1
-$(objtree)/rust/core.o: $$(RUST_LIB_SRC)/core/src/lib.rs FORCE
-	$(call if_changed_dep,rustc_library)
-
 $(objtree)/rust/compiler_builtins.o: private rustc_objcopy = -w -W '__*'
 $(objtree)/rust/compiler_builtins.o: $(srctree)/rust/compiler_builtins.rs \
     $(objtree)/rust/core.o FORCE
 	$(call if_changed_dep,rustc_library)
 
-$(objtree)/rust/alloc.o: private skip_clippy = 1
-$(objtree)/rust/alloc.o: $$(RUST_LIB_SRC)/alloc/src/lib.rs \
-    $(objtree)/rust/compiler_builtins.o FORCE
-	$(call if_changed_dep,rustc_library)
-
 $(objtree)/rust/build_error.o: $(srctree)/rust/build_error.rs \
     $(objtree)/rust/compiler_builtins.o FORCE
 	$(call if_changed_dep,rustc_library)
@@ -178,3 +168,14 @@ $(objtree)/rust/kernel.o: $(srctree)/rust/kernel/lib.rs $(objtree)/rust/alloc.o
     $(objtree)/rust/build_error.o \
     $(objtree)/rust/libmacros.so $(objtree)/rust/bindings_generated.rs FORCE
 	$(call if_changed_dep,rustc_library)
+
+# Targets that need to expand twice
+.SECONDEXPANSION:
+$(objtree)/rust/core.o: private skip_clippy = 1
+$(objtree)/rust/core.o: $$(RUST_LIB_SRC)/core/src/lib.rs FORCE
+	$(call if_changed_dep,rustc_library)
+
+$(objtree)/rust/alloc.o: private skip_clippy = 1
+$(objtree)/rust/alloc.o: $$(RUST_LIB_SRC)/alloc/src/lib.rs \
+    $(objtree)/rust/compiler_builtins.o FORCE
+	$(call if_changed_dep,rustc_library)