Ports: Make sure re-installing the gcc port doesn't fail

Re-installing the gcc port would previously fail because we failed to
overwrite the symlink.

Ports/gcc/package.sh

@@ -20,5 +20,5 @@ build() {
 
 install() {
     run make $installopts
-    run ln -s gcc "${SERENITY_INSTALL_ROOT}/usr/local/bin/cc"
+    run ln -sf gcc "${SERENITY_INSTALL_ROOT}/usr/local/bin/cc"
 }