Share common compilation flags

Makefile.in

@@ -84,8 +84,8 @@ LDFLAGS = @LDFLAGS@ $(LIBS)
 CPPFLAGS = @CPPFLAGS@ -I$(builddir) -I$(builddir)/include -I$(srcdir)/gnulib -I$(srcdir)/include -Wall -W \
 	 -DGRUB_LIBDIR=\"$(pkglibdir)\" -DLOCALEDIR=\"$(localedir)\"
 TARGET_CC = @TARGET_CC@
-TARGET_CFLAGS = @TARGET_CFLAGS@
-TARGET_ASFLAGS = @TARGET_ASFLAGS@
+TARGET_CFLAGS = -ffreestanding @TARGET_CFLAGS@
+TARGET_ASFLAGS = -nostdinc -fno-builtin @TARGET_ASFLAGS@
 TARGET_MODULE_FORMAT = @TARGET_MODULE_FORMAT@
 TARGET_APPLE_CC = @TARGET_APPLE_CC@
 OBJCONV = @OBJCONV@
@@ -93,9 +93,9 @@ TARGET_CPPFLAGS = @TARGET_CPPFLAGS@ -I$(srcdir)/include -I$(builddir) -I$(buildd
 ifneq ($(platform), emu)
 TARGET_CPPFLAGS += -nostdinc -isystem $(shell $(TARGET_CC) -print-file-name=include)
 endif
-TARGET_LDFLAGS = @TARGET_LDFLAGS@
+TARGET_LDFLAGS = -nostdlib @TARGET_LDFLAGS@
 TARGET_IMG_LDSCRIPT = @TARGET_IMG_LDSCRIPT@
-TARGET_IMG_LDFLAGS = @TARGET_IMG_LDFLAGS@
+TARGET_IMG_LDFLAGS = -nostdlib @TARGET_IMG_LDFLAGS@
 TARGET_IMG_CFLAGS = @TARGET_IMG_CFLAGS@
 TARGET_OBJ2ELF = @TARGET_OBJ2ELF@
 EXEEXT = @EXEEXT@