Compile OS specific files only once for all targets

OS specific files are not target dependent, so they can be compiled
once for all targets.
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

Makefile.objs

@@ -49,6 +49,8 @@ common-obj-y += $(net-obj-y)
 common-obj-y += $(qobject-obj-y)
 common-obj-$(CONFIG_LINUX) += $(fsdev-obj-$(CONFIG_LINUX))
 common-obj-y += readline.o console.o cursor.o async.o qemu-error.o
+common-obj-$(CONFIG_WIN32) += os-win32.o
+common-obj-$(CONFIG_POSIX) += os-posix.o
 
 common-obj-y += tcg-runtime.o host-utils.o
 common-obj-y += irq.o ioport.o input.o
@@ -144,8 +146,6 @@ hw-obj-$(CONFIG_ECC) += ecc.o
 hw-obj-$(CONFIG_NAND) += nand.o
 hw-obj-$(CONFIG_PFLASH_CFI01) += pflash_cfi01.o
 hw-obj-$(CONFIG_PFLASH_CFI02) += pflash_cfi02.o
-hw-obj-$(CONFIG_WIN32) += os-win32.o
-hw-obj-$(CONFIG_POSIX) += os-posix.o
 
 hw-obj-$(CONFIG_M48T59) += m48t59.o
 hw-obj-$(CONFIG_ESCC) += escc.o