Merge back ACPICA changes for v4.12.

drivers/acpi/acpica/Makefile

@@ -2,7 +2,7 @@
 # Makefile for ACPICA Core interpreter
 #
 
-ccflags-y			:= -Os -DBUILDING_ACPICA
+ccflags-y			:= -Os -D_LINUX -DBUILDING_ACPICA
 ccflags-$(CONFIG_ACPI_DEBUG)	+= -DACPI_DEBUG_OUTPUT
 
 # use acpi.o to put all files here into acpi.o modparam namespace