In b060076e21 ("cc-wrapper: broaden explicit libc++abi linking for
LLVM stdenv"), all packages started to be linked with -lc++abi. When
cross compiling, the libcxxabi path seemingly needs to be passed to the
the libtapi derivation; it won't pick it up on its own (perhaps because
of the bootstrapping?).
installTarget looks like a typo for installTargets. This causes a lot
of llvm and clang to be built and installed.
Clang is not intended to be an external dependency. The source bundle
includes llvm and clang. Adding include paths and building clangBasic
first is sufficient to use the internal clang components.
