Need to link with psapi.lib for GetProcessMemoryInfo (and skip -lrt on non-Linux)

toolkit/library/libxul-config.mk

@@ -99,8 +99,13 @@ STATIC_LIBS += \
   chromium_s \
   $(NULL)
 
+ifeq (Linux,$(OS_ARCH))
 OS_LIBS += -lrt
 endif
+ifeq (WINNT,$(OS_ARCH))
+OS_LIBS += psapi.lib
+endif
+endif
 
 STATIC_LIBS += \
 	xpcom_core \