Adding TARGET_CPU_VARIANT to config file.

Adding this since all arm builds will require TARGET_CPU_VARIANT
to be set to a valid value in the near future.

Merge from internal master.

Change-Id: I2b73f9dbdd04cd8ac47035875c714bd0e75920e7
diff --git a/target/board/generic/BoardConfig.mk b/target/board/generic/BoardConfig.mk
index 3b03250..35cbd27 100644
--- a/target/board/generic/BoardConfig.mk
+++ b/target/board/generic/BoardConfig.mk
@@ -20,6 +20,7 @@
 # application code generated with the NDK that uses NEON in the emulator.
 #
 TARGET_ARCH_VARIANT := armv7-a
+TARGET_CPU_VARIANT := generic
 TARGET_CPU_ABI := armeabi-v7a
 TARGET_CPU_ABI2 := armeabi