LLDB takes a reasonable amount of time to compile, but also isn't an
essential component of the LLVM suite.
Instead of always building it when we build clang, split it out into a
separate recipe.
On my build machine where clang takes 21 minutes to build with lldb, it
takes 19 minutes without lldb.
(From OE-Core rev: 9da4900aa5a37718bd42f277d5a1805ec897b1b4)
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
