configure: add test_ldflags function

This adds a test_ldflags function for testing linker flags without
adding them to LDFLAGS like check_ldflags does.

Originally committed as revision 21235 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -626,13 +626,18 @@ int x;
 EOF
 }
 
-check_ldflags(){
-    log check_ldflags "$@"
-    check_ld "$@" <<EOF && add_ldflags "$@"
+test_ldflags(){
+    log test_ldflags "$@"
+    check_ld "$@" <<EOF
 int main(void){ return 0; }
 EOF
 }
 
+check_ldflags(){
+    log check_ldflags "$@"
+    test_ldflags "$@" && add_ldflags "$@"
+}
+
 check_header(){
     log check_header "$@"
     header=$1