This has two main benefits:
* GHC will work reliably outside of stdenv, even when using -fllvm since
everything it'll call at runtime will be provided in PATH via the
wrapper scripts.
* LLVM will no longer leak into haskell packages' configure
scripts. This was an issue with llvm-hs which fails to build if the
LLVM version of the compiler since the propagatedBuildInputs of GHC
take precedence over the nativeBuildInputs added in the derivation.
This brings the binary GHCs on parity with the source built ones in
terms of the wrapper. The upshot of this is that compiling something
using the binary GHCs no longer depends on PATH being populated with
the tools included in stdenv at all. We can even test this by running
the installCheck with an empty environment (via `env -i`).
Copy the approach from the normal GHC derivations for adding an
`export PATH` into the scripts in `$out/bin` and use it to put the
specific LLVM version of the binary GHC into its PATH. This will
prevent the LLVM version of the GHC we are building later to take
precedence over the LLVM version this GHC needs.
Since we inherit the platform list from the bootstrap GHC, we get
differing lists depending on which platform we evaluate the platform
list on (depending on whether 8.10.2 or 8.6.5 is used). This leads to
Hydra thinking aarch64-linux is not supported as it evaluates on
x86_64-linux usually.
Since LLVM itself doesn't depend on target at all, this doesn't change
anything *in effect* (i. e. rebuild count should be zero), but it is
more clear about the intention and what LLVM is used for here (i. e. in
depsBuildTarget).
This means we only have to update the llvmPackages attribute in one
place now and should prevent situations like with 8.6.5 where different
versions would be used in the package set compared to the compiler
build.
Drop comments in the configuration-ghc-X.Y.x.nix files as well, since
LLVM version isn't tied to the compiler minor version at
all (e. g. 8.10.2 and 8.10.7 have different support ranges).
Without the fix build on ncurses-6.3 fails as:
src/include/souffle/provenance/Explain.h:522:18: error: format not a string literal and no format arguments [-Werror=format-security]
522 | mvwprintw(queryWindow, 1, 0, prompt.c_str());
| ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
