Add -lsocket -lnsl to APPLDFLAGS for solaris build

As suggested in GH-674

configure.ac

@@ -246,7 +246,7 @@ TESTLDADD=
 # Additional libraries required for programs under src directory.
 APPLDFLAGS=
 
-case "$host" in
+case "$host_os" in
   *android*)
     android_build=yes
     # android does not need -pthread, but needs followng 3 libs for C++
@@ -258,6 +258,12 @@ case "$host" in
     ;;
 esac
 
+case "$host_os" in
+  *solaris*)
+    APPLDFLAGS="$APPLDFLAGS -lsocket -lnsl"
+    ;;
+esac
+
 # zlib
 PKG_CHECK_MODULES([ZLIB], [zlib >= 1.2.3], [have_zlib=yes], [have_zlib=no])