doc: fix long line in BUILDING.md

Author: chasestarr

BUILDING.md

@@ -24,8 +24,8 @@ On OS X, you will also need:
     this under the menu `Xcode -> Preferences -> Downloads`
   * This step will install `gcc` and the related toolchain containing `make`
 
-* After building, you may want to setup [firewall rules](tools/macosx-firewall.sh) to avoid
-popups asking to accept incoming network connections when running tests:
+* After building, you may want to setup [firewall rules](tools/macosx-firewall.sh)
+to avoid popups asking to accept incoming network connections when running tests:
 
 ```console
 $ sudo ./tools/macosx-firewall.sh