Merge #14127: build: avoid getifaddrs when unavailable

9256f7d13f build: avoid getifaddrs when unavailable (Cory Fields)

Pull request description:

  These changes from @theuni help building when targeting platforms that don't always have getifaddrs available like Android < 24

Tree-SHA512: dbfeb83297bd6f00b7991f53eef8a04948d2d739bf47c0524d9ae5335b843b8a5c06ff98c109fe5e6192665e6d0cf58700b8aa7e2a0b410281d3c052881973ff

configure.ac

@@ -733,6 +733,10 @@ fi
 
 AC_CHECK_HEADERS([endian.h sys/endian.h byteswap.h stdio.h stdlib.h unistd.h strings.h sys/types.h sys/stat.h sys/select.h sys/prctl.h])
 
+AC_CHECK_DECLS([getifaddrs, freeifaddrs],,,
+    [#include <sys/types.h>
+    #include <ifaddrs.h>]
+)
 AC_CHECK_DECLS([strnlen])
 
 # Check for daemon(3), unrelated to --with-daemon (although used by it)

src/net.cpp

@@ -2167,7 +2167,7 @@ void Discover()
             }
         }
     }
-#else
+#elif (HAVE_DECL_GETIFADDRS && HAVE_DECL_FREEIFADDRS)
     // Get local host ip
     struct ifaddrs* myaddrs;
     if (getifaddrs(&myaddrs) == 0)