code: function installVersion(version) {
      return __awaiter(this, void 0, void 0, function () {
          return __generator(this, function (_a) {
              switch (_a.label) {
                  case 0:
                      if (!INSTALL_VERSIONS_CACHE[version]) return [3 /*break*/, 2];
                      return [4 /*yield*/, INSTALL_VERSIONS_CACHE[version]];
                  case 1:
                      _a.sent();
                      return [2 /*return*/, false];
                  case 2:
                      INSTALL_VERSIONS_CACHE[version] = _installVersion(version);
                      return [4 /*yield*/, INSTALL_VERSIONS_CACHE[version]];
                  case 3:
                      _a.sent();
                      return [2 /*return*/, true];
              }
          });
      });
  }
docs: install the given version into the ./solidity-version - folder
  returns false if already exists