depends: make LDFLAGS act like the other flags

depends/config.site.in

@@ -52,7 +52,9 @@ export PATH=$prefix/native/bin:$PATH
 export PKG_CONFIG="`which pkg-config` --static"
 export PKG_CONFIG_LIBDIR=$prefix/lib/pkgconfig
 export PKG_CONFIG_PATH=$prefix/share/pkgconfig
+
 export CPPFLAGS="-I$prefix/include/ $CPPFLAGS"
+export LDFLAGS="-L$prefix/lib $LDFLAGS"
 
 export CC="@CC@"
 export CXX="@CXX@"
@@ -84,4 +86,6 @@ fi
 if test -n "@CPPFLAGS@"; then
   export CPPFLAGS="@CPPFLAGS@ $CPPFLAGS"
 fi
-export LDFLAGS="-L$prefix/lib @LDFLAGS@ $LDFLAGS"
+if test -n "@LDFLAGS@"; then
+  export LDFLAGS="@LDFLAGS@ $LDFLAGS"
+fi