[Pal] Do not calculate .manifest.sgx.d dependencies during make clean

Pal/regression/Makefile

@@ -66,9 +66,11 @@ $(executables): %: %.c $(LDLIBS-executables)
 	$(call cmd,csingle)
 
 include $(wildcard *.d)
+ifeq ($(filter clean,$(MAKECMDGOALS)),)
 ifeq ($(SGX), 1)
 include $(addsuffix .manifest.sgx.d,$(executables))
 endif
+endif
 
 .lib/host_endian.h: ../src/host/$(PAL_HOST)/host_endian.h
 	@mkdir -p .lib

Pal/test/Makefile

@@ -53,9 +53,11 @@ $(executables): %: %.c $(LDLIBS)
 
 $(graphene_lib): .lib/host_endian.h
 	$(MAKE) -C ../lib target=$(abspath .lib)/
+ifeq ($(filter clean,$(MAKECMDGOALS)),)
 ifeq ($(SGX), 1)
 include $(addsuffix .manifest.sgx.d,$(executables))
 endif
+endif
 else
 .IGNORE: $(executables)
 $(executables):