Cplusplusify the constant MIN_RESTRICTED_HOME_SDK_VERSION

Make the former macro MIN_RESTRICTED_HOME_SDK_VERSION a constexpr.

Change-Id: I0e85a0edecbcb1f5bba95e14fc36cd9561b369a7
diff --git a/cmds/installd/commands.cpp b/cmds/installd/commands.cpp
index cd54de7..acc79fc 100644
--- a/cmds/installd/commands.cpp
+++ b/cmds/installd/commands.cpp
@@ -57,7 +57,7 @@
 static constexpr const char* kCpPath = "/system/bin/cp";
 static constexpr const char* kXattrDefault = "user.default";
 
-#define MIN_RESTRICTED_HOME_SDK_VERSION 24 // > M
+static constexpr const int MIN_RESTRICTED_HOME_SDK_VERSION = 24; // > M
 
 typedef int fd_t;