Switch installd to compile as C++.

This is the minimal change needed to switch it over to C++, which
paves the way for using more robust utilities like std::string.

Change-Id: I80ed6280146875eb6ddbbb340c05450388ca13f0
diff --git a/cmds/installd/Android.mk b/cmds/installd/Android.mk
index 8224e94..2d90ff3 100644
--- a/cmds/installd/Android.mk
+++ b/cmds/installd/Android.mk
@@ -1,6 +1,6 @@
 LOCAL_PATH := $(call my-dir)
 
-common_src_files := commands.c utils.c
+common_src_files := commands.cpp utils.cpp
 common_cflags := -Wall -Werror
 
 #
@@ -23,7 +23,7 @@
 LOCAL_MODULE := installd
 LOCAL_MODULE_TAGS := optional
 LOCAL_CFLAGS := $(common_cflags)
-LOCAL_SRC_FILES := installd.c $(common_src_files)
+LOCAL_SRC_FILES := installd.cpp $(common_src_files)
 LOCAL_SHARED_LIBRARIES := libcutils liblog libselinux
 LOCAL_STATIC_LIBRARIES := libdiskusage
 LOCAL_ADDITIONAL_DEPENDENCIES += $(LOCAL_PATH)/Android.mk