Fix build with newer Boost.

Index: libutil/src/System.cpp
--- libutil/src/System.cpp.orig
+++ libutil/src/System.cpp
@@ -251,7 +251,6 @@ bfs::path System::getExecutablePath()
 
 #undef AIX
 #undef AMIGAOS
-#undef ANDROID
 #undef BEOS
 #undef BSD
 #undef CYGWIN
@@ -271,7 +270,7 @@ bfs::path System::getExecutablePath()
 #undef BSD_NET
 #undef BSD_OPEN
 #define RTTR_BOOST_OS_LIST                                                                                                         \
-    (AIX)(AMIGAOS)(ANDROID)(BEOS)(BSD)(CYGWIN)(HPUX)(IRIX)(LINUX)(MACOS)(OS400)(QNX)(SOLARIS)(UNIX)(SVR4)(VMS)(WINDOWS)(BSD_BSDI)( \
+    (AIX)(AMIGAOS)(BEOS)(BSD)(CYGWIN)(HPUX)(IRIX)(LINUX)(MACOS)(OS400)(QNX)(SOLARIS)(UNIX)(SVR4)(VMS)(WINDOWS)(BSD_BSDI)( \
       BSD_DRAGONFLY)(BSD_FREE)(BSD_NET)(BSD_OPEN)
 
 #undef BORLAND
