llvmPackages_{12,13,14,15,16,17,git}.{libcxx,libcxxabi}: merge libcxxabi into libcxx (#292043)

- merge libcxxabi into libcxx for LLVM 12, 13, 14, 15, 16, 17, and git.
- remove the link time workaround `-lc++ -lc++abi` from 58 packages as it is no longer required.
- fixes https://github.com/NixOS/nixpkgs/issues/166205
- provides alternative fixes for. https://github.com/NixOS/nixpkgs/issues/269548 https://github.com/NixOS/nix/issues/9640
- pkgsCross.x86_64-freebsd builds work again

This change can be represented in 3 stages
1. merge libcxxabi into libcxx -- files: pkgs/development/compilers/llvm/[12, git]/{libcxx, libcxxabi}
2. update stdenv to account for merge -- files: stdenv.{adapters, cc.wrapper, darwin}
3. remove all references to libcxxabi outside of llvm (about 58 packages modified)

### merging libcxxabi into libcxx
- take the union of the libcxxabi and libcxx cmake flags
- eliminate the libcxx-headers-only package - it was only needed to break libcxx <-> libcxxabi circular dependency
- libcxx.cxxabi is removed. external cxxabi (freebsd) will symlink headers / libs into libcxx.
- darwin will re-export the libcxxabi symbols into libcxx so linking `-lc++` is sufficient.
- linux/freebsd `libc++.so` is a linker script `LINK(libc++.so.1, -lc++abi)` making `-lc++` sufficient.
- libcxx/default.nix [12, 17] are identical except for patches and `LIBCXX_ADDITIONAL_LIBRARIES` (only used in 16+)
- git/libcxx/defaul.nix  does not link with -nostdlib when useLLVM is true so flag is removed. this is not much different than before as libcxxabi used -nostdlib where libcxx did not, so libc was linked in anyway.

### stdenv changes
- darwin bootstrap, remove references to libcxxabi and cxxabi
- cc-wrapper: remove c++ link workaround when libcxx.cxxabi doesn't exist (still exists for LLVM pre 12)
- adapter: update overrideLibcxx to account for a pkgs.stdenv that only has libcxx

### 58 package updates
- remove `NIX_LDFLAGS = "-l${stdenv.cc.libcxx.cxxabi.libName}` as no longer needed
- swift, nodejs_v8 remove libcxxabi references in the clang override

https://github.com/NixOS/nixpkgs/pull/292043

1 files changed, 0 insertions, 5 deletions

diff --git a/pkgs/by-name/us/usql/package.nix b/pkgs/by-name/us/usql/package.nix
index 7c0b093dfffc8..21a5bc99e67ba 100644
--- a/pkgs/by-name/us/usql/package.nix
+++ b/pkgs/by-name/us/usql/package.nix
@@ -50,11 +50,6 @@ buildGoModule rec {
     "no_adodb"
   ];
 
-  # Work around https://github.com/NixOS/nixpkgs/issues/166205.
-  env = lib.optionalAttrs stdenv.cc.isClang {
-    NIX_LDFLAGS = "-l${stdenv.cc.libcxx.cxxabi.libName}";
-  };
-
   ldflags = [
     "-s"
     "-w"