Revert "libcxx: add linker scripts for libc++.a to ensure libc++abi.a is properly linked"

This reverts commit 72e1764199805ab6e602fa3762a4d95bfdf80cb8.

This causes the GHC panic reported in issue #55848.

pkgs/development/compilers/llvm/4/libc++/default.nix

···
 
   linkCxxAbi = stdenv.isLinux;
 
-  postInstall = ''
-    mv $out/lib/libc++.a $out/lib/libc++_static.a
-    cp ${./libc++.a} $out/lib/libc++.a
-  '';
-
   setupHooks = [
     ../../../../../build-support/setup-hooks/role.bash
     ./setup-hook.sh

pkgs/development/compilers/llvm/4/libc++/libc++.a

···
-INPUT(-lc++_static -lc++abi)

pkgs/development/compilers/llvm/5/libc++/default.nix

···
 
   linkCxxAbi = stdenv.isLinux;
 
-  postInstall = ''
-    mv $out/lib/libc++.a $out/lib/libc++_static.a
-    cp ${./libc++.a} $out/lib/libc++.a
-  '';
-
   setupHooks = [
     ../../../../../build-support/setup-hooks/role.bash
     ./setup-hook.sh

pkgs/development/compilers/llvm/5/libc++/libc++.a

···
-INPUT(-lc++_static -lc++abi)

pkgs/development/compilers/llvm/6/libc++/default.nix

···
 
   linkCxxAbi = stdenv.isLinux;
 
-  postInstall = ''
-    mv $out/lib/libc++.a $out/lib/libc++_static.a
-    cp ${./libc++.a} $out/lib/libc++.a
-  '';
-
   setupHooks = [
     ../../../../../build-support/setup-hooks/role.bash
     ./setup-hook.sh

pkgs/development/compilers/llvm/6/libc++/libc++.a

···
-INPUT(-lc++_static -lc++abi)

pkgs/development/compilers/llvm/7/libc++/default.nix

···
 
   linkCxxAbi = stdenv.isLinux;
 
-  postInstall = ''
-    mv $out/lib/libc++.a $out/lib/libc++_static.a
-    cp ${./libc++.a} $out/lib/libc++.a
-  '';
-
   setupHooks = [
     ../../../../../build-support/setup-hooks/role.bash
     ./setup-hook.sh

pkgs/development/compilers/llvm/7/libc++/libc++.a

···
-INPUT(-lc++_static -lc++abi)