solc: remove 0.7 release

They're failing on Hydra, the workload to keep them working is not worth it.

pkgs/development/compilers/solc/0.7.nix

@@ -1,78 +0,0 @@
-{ lib, gccStdenv, fetchzip, boost, cmake, ncurses, python3, coreutils
-, z3Support ? true, z3 ? null, cvc4Support ? true, cvc4 ? null
-, cln ? null, gmp ? null
-}:
-
-# compiling source/libsmtutil/CVC4Interface.cpp breaks on clang on Darwin,
-# general commandline tests fail at abiencoderv2_no_warning/ on clang on NixOS
-
-assert z3Support -> z3 != null && lib.versionAtLeast z3.version "4.6.0";
-assert cvc4Support -> cvc4 != null && cln != null && gmp != null;
-
-let
-  jsoncppVersion = "1.9.4";
-  jsoncppUrl = "https://github.com/open-source-parsers/jsoncpp/archive/${jsoncppVersion}.tar.gz";
-  jsoncpp = fetchzip {
-    url = jsoncppUrl;
-    sha256 = "0qnx5y6c90fphl9mj9d20j2dfgy6s5yr5l0xnzid0vh71zrp6jwv";
-  };
-in
-gccStdenv.mkDerivation rec {
-
-  pname = "solc";
-  version = "0.7.4";
-
-  # upstream suggests avoid using archive generated by github
-  src = fetchzip {
-    url = "https://github.com/ethereum/solidity/releases/download/v${version}/solidity_${version}.tar.gz";
-    sha256 = "02261l54jdbvxk612z7zsyvmchy1rx4lf27b3f616sd7r56krpkg";
-  };
-
-  postPatch = ''
-    substituteInPlace cmake/jsoncpp.cmake \
-      --replace "${jsoncppUrl}" ${jsoncpp}
-  '';
-
-  cmakeFlags = [
-    "-DBoost_USE_STATIC_LIBS=OFF"
-  ] ++ lib.optionals (!z3Support) [
-    "-DUSE_Z3=OFF"
-  ] ++ lib.optionals (!cvc4Support) [
-    "-DUSE_CVC4=OFF"
-  ];
-
-  nativeBuildInputs = [ cmake ];
-  buildInputs = [ boost ]
-    ++ lib.optionals z3Support [ z3 ]
-    ++ lib.optionals cvc4Support [ cvc4 cln gmp ];
-  checkInputs = [ ncurses python3 ];
-
-  # Test fails on darwin for unclear reason
-  doCheck = gccStdenv.hostPlatform.isLinux;
-
-  checkPhase = ''
-    while IFS= read -r -d ''' dir
-    do
-      LD_LIBRARY_PATH=$LD_LIBRARY_PATH''${LD_LIBRARY_PATH:+:}$(pwd)/$dir
-      export LD_LIBRARY_PATH
-    done <   <(find . -type d -print0)
-
-    pushd ..
-    # IPC tests need aleth avaliable, so we disable it
-    sed -i "s/IPC_ENABLED=true/IPC_ENABLED=false\nIPC_FLAGS=\"--no-ipc\"/" ./scripts/tests.sh
-    for i in ./scripts/*.sh ./scripts/*.py ./test/*.sh; do
-      patchShebangs "$i"
-    done
-    TERM=xterm ./scripts/tests.sh
-    popd
-  '';
-
-  meta = with lib; {
-    description = "Compiler for Ethereum smart contract language Solidity";
-    homepage = "https://github.com/ethereum/solidity";
-    license = licenses.gpl3;
-    platforms = with platforms; linux; # darwin is currently broken
-    maintainers = with maintainers; [ dbrock akru lionello sifmelcara ];
-    inherit version;
-  };
-}

pkgs/top-level/all-packages.nix

@@ -11679,9 +11679,7 @@ in
 
   smlpkg = callPackage ../tools/package-management/smlpkg { };
 
-  solc = solc_0_8;
-  solc_0_8 = callPackage ../development/compilers/solc { };
-  solc_0_7 = callPackage ../development/compilers/solc/0.7.nix { };
+  solc = callPackage ../development/compilers/solc { };
 
   souffle = callPackage ../development/compilers/souffle {
     autoreconfHook = buildPackages.autoreconfHook269;