Rename protoc to aprotoc.

With gLucid protoc is installed in the base system, by renaming
our version there will be no confusion about which compiler is
being used.

Change-Id: Id6900baacc7d57abee5dc5f694b013d7a42b35c6
diff --git a/core/config.mk b/core/config.mk
index e2459f6..5805607 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -203,7 +203,7 @@
 DOXYGEN:= doxygen
 AAPT := $(HOST_OUT_EXECUTABLES)/aapt$(HOST_EXECUTABLE_SUFFIX)
 AIDL := $(HOST_OUT_EXECUTABLES)/aidl$(HOST_EXECUTABLE_SUFFIX)
-PROTOC := $(HOST_OUT_EXECUTABLES)/protoc$(HOST_EXECUTABLE_SUFFIX)
+PROTOC := $(HOST_OUT_EXECUTABLES)/aprotoc$(HOST_EXECUTABLE_SUFFIX)
 ICUDATA := $(HOST_OUT_EXECUTABLES)/icudata$(HOST_EXECUTABLE_SUFFIX)
 SIGNAPK_JAR := $(HOST_OUT_JAVA_LIBRARIES)/signapk$(COMMON_JAVA_PACKAGE_SUFFIX)
 MKBOOTFS := $(HOST_OUT_EXECUTABLES)/mkbootfs$(HOST_EXECUTABLE_SUFFIX)