For each link given as http://, verify that the site is accessible over
https:// and, if so, switch to it. These domains were converted:
* llvm.org
* clang.llvm.org
* en.cppreference.com
* www.dxx-rebirth.com
* www.libsdl.org
* www.scons.org
Vendor library has new names to avoid conflicts with Mesa. Update
raspberrypi argument to use new libraries and support Mesa VC4 driver.
* raspberrypi=1 will build against the (newly named) vendor libraries
* raspberrypi=mesa will target building against the VC4 driver.
Both will select GLES by default, but you can target GL for the VC4 driver
via "raspberrypi=mesa opengles=0"